Organics on Mars?
Inge L. ten Kate
Organics are expected to exist on Mars based on meteorite infall, in situ production, and any possible biological
sources. Yet they have not been detected on the martian surface; are they there, or are we not capable enough to
detect them? The Viking gas chromatograph–mass spectrometer did not detect organics in the headspace of
heated soil samples with a detection limit of parts per billion. This null result strongly inﬂuenced the inter-
pretation of the reactivity seen in the Viking biology experiments and led to the conclusion that life was not
present and, instead, that there was some chemical reactivity in the soil. The detection of perchlorates in the
martian soil by instruments on the Phoenix lander and the reports of methane in the martian atmosphere suggest
that it may be time to reconsider the question of organics. The high-temperature oxidizing properties of per-
chlorate will promote combustion of organics in pyrolytic experiments and may have affected the ability of both
Phoenix’s organic analysis experiment and the Viking mass spectrometer experiments to detect organics. So the
question of organics on Mars remains open. A primary focus of the upcoming Mars Science Laboratory will be
the detection and identiﬁcation of organic molecules by means of thermal volatilization, followed by gas
chromatography–mass spectrometry—as was done on Viking. However, to enhance organic detectability, some
of the samples will be processed with liquid derivatization agents that will dissolve organics from the soil before
pyrolysis, which may separate them from the soil perchlorates. Nonetheless, the problem of organics on Mars is
not solved, and for future missions other organic detection techniques should therefore be considered as well.
Key Words: Mars—Organic degradation—Search for Mars organics—Laboratory investigations—Interpretation
of planetary mission data. Astrobiology 10, 589–603.
Organic molecules have been detected in the interstellar
medium (Ehrenfreund and Charnley, 2000; Millar, 2004;
and references in both), comets (see Crovisier, 2004, for a re-
view), meteorites (Botta and Bada, 2002; Sephton, 2002; and
references in both), and interplanetary dust particles (Flynn,
1996), and are highly abundant on Earth. Mars seems to be a
next logical place to search for organic material in that Mars
experienced a long history of bombardment (Marcus, 1968;
Werner, 2008) by comets, meteorites [an estimated yearly
accumulation rate of 510
meteorites greater than
10 g in mass per square kilometer (Bland and Smith, 2000)],
and dust particles. The total mass accretion rate by comets,
meteorites, and dust particles is estimated between 1.810
per year (Flynn and McKay, 1990), which
corresponds to an annual arrival of organic material at the
martian surface on the order of 10
kg (Flynn, 1996). Another
possible source of organic matter is through production on, or
beneath, the martian surface. Several mechanisms for en-
dogenous production of organic material on early Earth have
been suggested, which may have played a role on early Mars
as well, such as lightning, coronal discharge, UV radiation,
and atmospheric shocks (Chyba and Sagan, 1992). Even
though the presence of organics on Mars seems likely, based
on the above, organic matter has not yet been detected on the
martian surface. Is it there at all, or are investigators simply
incapable of detecting it? In this paper, I offer an overview of
the search for organics on Mars by the Viking mission and, to
a lesser extent, the Phoenix mission; the conclusions drawn, in
particular, from the Viking mission; and the ways in which
these conclusions have shaped laboratory studies on organics
under martian environmental conditions.
2. Before the Viking Mission
By the early 1970s, several missions had visited the planet
Mars with varying results. Data obtained by Mariner 4 in
1964 and Mariners 6 and 7 in 1969 caused pessimism about
the possibility of life on Mars (Klein, 1974). However, the
Mariner 9 orbiter and its terrestrial observations showed that
(1) Mars is a geologically active planet; (2) the 3–10 mbar
NASA Goddard Space Flight Center, Greenbelt, Maryland, and Goddard Earth Science and Technology Center, University of Maryland,
Baltimore County, Baltimore, Maryland.
Volume 10, Number 6, 2010
ªMary Ann Liebert, Inc.
atmosphere is primarily composed of CO
amounts of CO, O
O, and some other traces gases, in-
cluding O (Barker, 1972); (3) there is 10–20 mm precipitable
water; and (4) the surface contains about 1% H
Mars, 1973; Oro
´and Flory, 1973). Present martian atmo-
spheric chemical conditions are believed to be hostile with
respect to abiotic organic synthesis, but conditions may have
been favorable in the distant past (Fanale, 1971). Laboratory
simulations have indicated that relatively simple organic
compounds could be produced by the direct interaction of
UV radiation with the martian atmosphere (Young et al.,
1965) in the presence of catalytic surfaces (Hubbard et al.,
1971, 1973). Tyson and Oyama (1973) showed that CO
be incorporated into already present amino acids under
simulated martian radiation conditions. More-complex or-
ganics are known to be present in carbonaceous chondrites
(Anders, 1964; Oro
´, 1972; Nagy, 1975), and Dycus (1969)
calculated the mass loss of meteorites that occurs while they
travel through the atmosphere and the mass of meteorites
after impact on the martian surface, his ﬁndings implying
that it is likely organic matter has been delivered to the
martian surface over the course of billions of years. Since the
Mariner missions were not designed to look for organic
material or small forms of life (such as microorganisms) and
could only scan the surface remotely, the Viking mission was
launched in 1975 to land on Mars and analyze the surface.
3. The Viking Mission
The Viking mission consisted of two spacecraft, Viking 1
and Viking 2, each composed of an orbiter and a lander and
carrying a range of instruments designed for analysis of soil,
rock, and atmosphere (Soffen, 1977). On July 20, 1976, the
Viking 1 lander landed at Chryse Planitia (22.488N, 49.978W).
The Viking 2 lander landed at Utopia Planitia (47.978N,
225.748W) on September 3, 1976. Biemann et al. (1977) de-
scribed the aim of the Viking mission as follows:
One of the major goals of the Viking mission was to ﬁnd
out whether or not organic compounds exist on the sur-
face of the planet Mars and, if they do exist, to determine
their structures and measure their abundances. This
seemed important because we hoped that the nature of
martian organic molecules would provide a sensitive in-
dicator of the chemical and physical environment in
which they were formed. Furthermore, we hoped that the
details of their structures would indicate which of many
possible biotic and abiotic syntheses are occurring on
For this purpose, the Viking landers were equipped with a
biological and a molecular analysis experiment (Soffen,
3.1. The Viking molecular analysis experiment
The molecular analysis experiment, also known as the
Viking gas chromatograph–mass spectrometer (GCMS), was
designed to heat soil samples to 2008C, 3508C, and 5008C,
and analyze the gases that were released upon heating. The
molecular analysis experiment had the following goals
(Anderson et al., 1972):
(1) A qualitative and semi-quantitative determination of
the organic compounds present in the top 10 cm layer of
the surface of Mars; (2) qualitative and quantitative
composition (including isotope abundances) of the at-
mosphere at the surface; (3) semi-quantitative determi-
nation of water (and its physical state, if possible) in the
surface; and (4) whatever information on the inorganic
(mineralogical) composition of the surface that can be
obtained in the course of the measurements performed to
satisfy (1)–(3) above.
The released gases were subsequently analyzed by a gas
chromatographic column-detector system, a mass spec-
trometer with a range of 12–200 dalton, or a combination of
both in which the mass spectrometer served as a detector for
the gas chromatograph. Direct atmospheric measurements
were made with the mass spectrometer (Anderson et al.,
1972). The detection limits of the GCMS were in the parts per
billion range for compounds containing more than two car-
bon atoms and in the parts per million range for compounds
containing one or two carbon atoms (Biemann, 1979). In the
four samples taken from surface and subsurface material
from both landing sites, water (0.1–1.0 wt%), carbon dioxide
(0.05–0.6 ppm), and some organics were detected, including
benzene and toluene. Furthermore, Viking 1 detected traces
of chloromethane at 15 ppb at 2008C and Viking 2 detected
dichloromethane at 0.04–40 ppb at 200–5008C. However,
these chlorohydrocarbons were all considered to be terres-
trial contaminants, although they had not been detected
at those levels in the blank runs. Therefore, the conclusion
was drawn that no organic compounds of martian origin
were detected (Biemann et al., 1976, 1977).
3.2. The Viking biology investigations
The Viking biology instrument was equipped with three
experiments that could test four different hypotheses: (i) an
active martian metabolism is limited by the availability of
water; (ii) biological activity is best detected under condi-
tions that approximate those on Mars; (iii) an active martian
metabolism (the chemical reactions in a cell that convert
‘‘food’’ into energy) is heterotrophic (in need of an external
source of ‘‘food’’) and uses a very dilute aqueous solution
of simple organic compounds; and (iv) an active martian
metabolism is heterotrophic and uses a concentrated mixture
of many organic compounds (Klein, 1977). The Viking bi-
ology package included a gas exchange (GEx) experiment
(Oyama and Berdahl, 1977) that measured the production of
, and O
and the uptake of CO
samples; a pyrolytic release (PR) or carbon assimilation ex-
periment (Horowitz et al., 1977) that measured the incorpo-
ration of carbon-14 (
C, radioactive carbon) from
into organic matter; and a labeled release (LR) ex-
periment (Levin and Straat, 1977) that measured the pro-
C labeled gas upon addition of nutrient containing
C labeled organics. Table 1 gives an overview of the three
experiments and their results.
The GEx experiment consisted of an 8.5 cm
sample cell that
could be heated and two gas chromatographic columns with
two thermal conductivity detectors, which could measure
, Ne, N
, Ar or CO, NO, CH
, Kr, CO
O, and H
(Oyama et al., 1976; Oyama and Berdahl, 1977). Soil samples
were incubated in the presence of Mars atmo-
sphere in the cell that was ﬁlled up to 200 mbar with a test
gas composed of additional CO
, Kr, and He. This higher
590 TEN KATE
pressure was necessary for the gas to be sampled into the gas
chromatographic columns. The experiment tested two hypo-
theses and an aqueous nutrient solution described in Oyama
et al. (1976). The ﬁrst hypothesis was based on the assump-
tion that nutrients were already present in the martian soil
and that martian organisms only needed water to grow.
Therefore, in the humid, non-nutrient mode a small amount
) of the nutrient solution was added in such a way
that the solution would not touch the soil but would only
saturate the atmosphere with water. This way the soil would
only be humidiﬁed by the atmospheric water in the cell, and
no interaction with the nutrients would take place. The at-
mosphere was then analyzed to measure the generation and
loss (desorption) of gases. Nonbiological activity was dif-
ferentiated from biological activity by repetitive charges of
fresh medium and prolonged incubation cycles (Oyama,
1972). The second hypothesis assumed that organisms on
Mars are heterotrophic. This was tested in the wet mode,
where enough (*2cm
) nutrient solution was added to the
soil sample to wet the soil and let it interact with the nutrient.
The samples were incubated for 0.1 to 103 sols (martian days;
0.1 to 106 Earth days). During the incubation, the gas chro-
matographs analyzed the atmosphere in the cell to measure
the production of CO
, and O
and the uptake
by soil samples (Oyama and Berdahl, 1977). The re-
sults showed that, upon both humidiﬁcation and wetting of
the soil samples, an immediate release of N
, and Ar
was measured. The release of N
, and Ar was associ-
ated with surface desorption caused by water, and the O
release with decomposition of superoxides (O
2) inferred to
be present in the soil (Ballou et al., 1978). When fresh nutrient
solution and test gas were added to the wet samples, only
was released, but at a rate that decreased
with each recharge (Oyama and Berdahl, 1977). If microor-
ganisms had been present, a recharge of the samples with
fresh nutrient solution would have led to a similar gas pro-
duction, assuming they had survived the ﬁrst dose of nu-
trient. This CO
evolution in the wet samples was, therefore,
thought to have come from the oxidation of organics present
in the nutrient by g-Fe
in the surface samples (Oyama and
Berdahl, 1977). A control experiment with a sterilized sam-
ple, which was heated to 1458C for 3.5 h, was conducted and
also showed the release of O
. From these results, the overall
conclusion clearly excluded a biological explanation of the
results (Oyama and Berdahl, 1977).
The PR experiment or carbon assimilation was designed to
detect life in the martian soil by measuring the incorpora-
tion of carbon-14 from
into organic matter
Table 1. The Viking Biology Experiment
Experiment Measurement Nutrients added
added Illumination Results
None None Light and
None Trace Light and
Heating to 908C has
hardly any effect.
Heating to 1758C
reduced yield by
Gas Exchange Production of CO
, and O
the uptake of CO
by soil samples
None Moist Dark Release of some CO
, and Ar
Rapid release of O
of organic and
Same as moist
Labeled Release Production of
gas upon addition of
of simple organic
C-bearing gas produced
Heating to 188C had
Heating to 40–508C
Heating to 1608C stopped
Storage at 108C for
4 months stopped
Adapted from Klein, 1977.
Horowitz et al., 1972.
Horowitz et al., 1976, 1977.
Oyama and Berdahl, 1977.
Levin and Straat, 1976a.
Levin and Straat, 1976b.
Levin and Straat, 1977.
Levin and Straat, 1979.
ORGANICS ON MARS? 591
(Horowitz et al., 1972). The experiment was based on the
hypothesis that potential martian life, like terrestrial life, is
carbon based and exchanges carbon with the atmosphere. The
experiment consisted of a closed sample cell with a window
and a heater, a trapping column, and a radiation detector. A
sample was inserted into the sample cell together with cap-
tured martian atmosphere, which was enriched with *20 ml
(ratio 2:98). Some samples were illumi-
nated with a xenon lamp during incubation to simulate sun-
light, while others were left in the dark. After an incubation
time of 120 h, the cell was heated to 1208C and vented to
remove the nonreacted
. The cell was then
heated to 6358C to pyrolyze potential organic compounds and
that was adsorbed onto the soil. This
gas passed through a column, which trapped potential or-
ganics, but the adsorbed
, the ‘‘pyrolysis
,’’ continued into the radiation detector for analysis. By
heating the trap to 7008C, the ‘‘trapped organics’’ were re-
leased and oxidized into CO
, and subsequently analyzed in
the radiation detector as well. If
similated by martian microorganisms, they would appear in
the analysis of the ‘‘trapped organics’’ (Horowitz et al., 1972,
1977). The results showed that the amount of ﬁxed carbon-14
was small compared to terrestrial standards and that illumi-
nated samples seemed to have produced the highest carbon-
14 yields. Furthermore, multiple samples from the same scoop
of soil were analyzed: one sample directly after retrieval and
the others after a period of storage at elevated temperatures.
Data from these samples showed that heating the surface
material to 908C for nearly 2 h had no effect on the reaction,
but heating to 1758C for 3 h reduced the reaction by nearly
90% (Horowitz et al., 1976, 1977; Hubbard, 1976). Initially, the
results of the PR experiments were explained as weak but
signiﬁcant presumptive positives (Horowitz et al., 1976).
However, later laboratory experiments designed to reproduce
and further explain these results appeared to rule out a bio-
logical explanation. In combination with results from the other
biological as well as the molecular analysis experiments, it
was concluded that it is unlikely that the reaction is biological
(Horowitz et al., 1977).
The LR experiment was based on radiorespirometry, a
technique in which a
C radioactively labeled nutrient so-
lution is added to a sample, in this case martian soil, in a
closed environment (sample cell), and any radioactive car-
bon dioxide subsequently detected in the atmosphere in the
cell is used as evidence for the presence of life (see below).
The experiment consisted of four incubation cells, a nutrient
reservoir, and two solid-state beta detectors, and was de-
signed to measure carbon-14 produced by potential micro-
organisms (Levin and Straat, 1976a). The assumptions on
which the experiment was based were (Levin, 1972) (a) al-
though possible life on Mars may not be limited to micro-
organisms, the latter must be present to accomplish the
biodegradation required for recycling of the organic matter;
(b) the biochemical reactions at the cellular level are aqueous;
(c) the organisms assimilate compounds from their envi-
ronment and produce gas as an end product; (d) such com-
pounds include any or all of the following: relatively simple
carbon molecules, ions, sulfate. First LR results showed—at
both landing sites—rapid evolution of radioactive counts
upon addition of the nutrient to a fresh surface sample (Le-
vin and Straat, 1976b). Analysis of a second set of samples
showed a similar behavior. In summary, the initial produc-
tion of gas from the LR nutrient was uniform; when the
reaction approached completion, addition of more nutrient
resulted in a net loss of the carbon-14 labeled gas. Further-
more, when the samples were heated to moderate tempera-
tures (40–508C) the reaction slowed down, whereas raising
the temperature to 1608C caused the reaction to end. In
contrast, exposure to 188C for 2 sols (1 sol ¼1 martian
day &24.6 Earth hours) did not appear to affect the reaction
(Levin and Straat, 1977). The ﬁnal experiments, which in-
volved two soil samples that were stored at the spacecraft at
*108C for several months, showed that the reactions had
strongly diminished (Levin and Straat, 1979). The ﬁrst con-
clusion drawn from these experiments was that ‘‘the results
are consistent with a biological response and also greatly
narrow the number of possible chemical reactants’’ (Levin
and Straat, 1977). Later, laboratory experiments showed that
addition of hydrogen peroxides might have led to similar
results as measured on the martian surface. These laboratory
results, however, were only obtained in the presence of
certain minerals, some of which are not found on Mars, and
assumed a much higher hydrogen peroxide content than had
been measured up to then in the martian atmosphere. This
led to the conclusion that ‘‘the presence of a biological agent
on Mars must still be considered’’ (Levin and Straat, 1981).
3.3. Overall conclusions
The main conclusions drawn from the experiments were
that there is neither organic material nor life present on the
surface of Mars at the two Viking landing sites. ‘‘The molecular
analysis experiment has demonstrated the absence of organic
compounds in the surface material at two Viking sites. This
fact has had a very important impact on the interpretation of
the data received from the biology experiments (Klein, 1977;
Klein et al., 1976) and put some boundaries on the chemical
and physical environment at the surface’’ (Biemann, 1979). The
biology experiments were then interpreted by Klein (1977) as
follows: ‘‘For each experiment, except for the LR experiment,
we must conclude that there were no organisms present within
the limits of detectability for these experiments and that all of
the observed reactions for these were the results of nonbio-
logical phenomena.’’ However, Klein (1977) then continued,
‘‘we must not overlook the fact, in assessing the probabilities of
life on Mars, that all of our experiments were conducted under
conditions that deviated to varying extents from ambient
martian conditions, and while we have accumulated data,
these and their underlying mechanisms may all be coincidental
and not directly relevant to the issue of life on that planet.’’
4. Now What?
Although there were many indications that pointed to-
ward the presence of at least organic material on the surface
of Mars (as described in the Introduction), Viking did not
ﬁnd them. Absence of evidence, however, is not evidence of
absence, and a wealth of papers has argued for reasons of
nondetection of organics by this mission. These papers can
roughly be divided into two categories, (1) studies that fo-
cused on the ability of the Viking instruments and techniques
to detect organic matter on the martian surface, and (2)
laboratory simulations in which the effects of Mars’ envi-
ronmental conditions, as well as soil composition and min-
592 TEN KATE
eralogy, on organic matter are studied (see Table 2 for an
overview). In 2009, two signiﬁcant events brought new evi-
dence to the search for organics on Mars.
(a) Instruments on the Phoenix lander detected perchlo-
rates in the martian soil (Hecht et al., 2009).
(b) New results (Mumma et al., 2009) on the presence of
methane in the martian atmosphere conﬁrmed earlier
observations (Formisano et al., 2004; Geminale et al.,
2008) that this methane varies both geographically and
seasonally, implying a faster production and destruc-
tion rate than assumed before.
These events, described in more detail in Section 5, spurred a
new wave of laboratory investigations. In Section 6, I will
ﬁrst describe the studies that focus on the ability of the Vi-
king instruments and techniques to detect organic matter on
the martian surface. In Section 7, I will give an overview of
the laboratory studies in which organic material was inves-
tigated under simulated martian conditions; and, in Section
8, I will make some concluding remarks. Another category of
research that evolved after Viking focused on microorgan-
isms and potential life on Mars. These studies fall outside the
scope of this paper; for overviews of this category see, for
example, Jensen et al. (2008) and Schuerger and Clark (2008).
5. Methane and Perchlorates
In 2004, Formisano et al. (2004) and Krasnopolsky et al.
(2004) published works on the detection of methane in the
martian atmosphere, although they used different methods
and obtained different mixing ratios. Formisano et al. (2004)
measured a variable amount of 0–30 ppbv, with a global
average of 10 5 ppbv from orbit (the Planetary Fourier
Spectrometer, on board Mars Express), whereas Krasno-
polsky et al. (2004) measured 10 3 ppbv from an Earth-
based telescope. The photochemical lifetime of methane was
modeled to be 300–600 years (Wong et al., 2003), a lifetime
also used by Krasnopolsky et al. (2004) to explain their ob-
servations. The potential variation in the observations of
Formisano et al. (2004) is, however, more difﬁcult to explain
photochemically and points toward localized sources or
sinks. Additional Planetary Fourier Spectrometer observa-
tions showed an even stronger seasonal variation, which
could not be explained photochemically (Geminale et al.,
2008). Earth-based observations by Mumma et al. (2009)
conﬁrmed this seasonal variation and showed a mixing ratio
of nearly 0 ppb in the early northern spring to 45 ppb in the
late northern summer. Assuming a cyclic, and not sporadic,
seasonal cycle, Mumma et al. (2009) derived a production
(from equinox to summer) and loss (from summer to equi-
nox) rate of methane of 0.5 kg s
. However, photochemistry
alone is not enough to explain the seasonal variation of
methane. Modeling results have suggested that dust-induced
electrochemistry can signiﬁcantly increase the destruction
rate of methane, both via direct dissociation and the en-
hanced production of OH- and H- (Farrell et al., 2006). At
electric ﬁelds above 10 kV m
, the destruction of methane is
more efﬁcient through electrochemistry than photochemis-
try. Both destruction processes have, however, been sug-
gested not to be effective enough to explain the seasonal
variation, which suggests an extraordinarily harsh environ-
ment for the survival of organics on the planet (Lefe
Forget, 2009). Methane-producing processes at work on the
martian surface may explain the methane observation by
Mumma et al. (2009). The presence of biology was suggested
by Krasnopolsky et al. (2004) as a possible methane-producing
process, but there are numerous abiological processes to
consider as well. Recent volcanism (Neukum et al., 2004)
could be a minor source, although only a few hot spots have
been observed by the Thermal Emission Imaging System
(THEMIS) on the Mars Odyssey orbiter (Christensen et al.,
2003, 2005), and sulfur dioxide, the gaseous counterpart of
volcanic methane, has only been observed in trace amounts
(Krasnopolsky, 2005). Another process could be the serpen-
tinization of ultramaﬁc crust whereby methane is formed in
the presence of limited amounts of water and CO
, with FeO
as a catalyst (Palandri and Reed, 2004). Serpentinization re-
quires temperatures of 40–908C, which are believed to occur
at a depth of as little as 2 km, and stable liquid water, which
occurs at depths of 2–20 km (Oze and Sharma, 2005; Atreya
et al., 2007). Exogenous sources of methane, from comets and
meteorites, have also been considered (Court and Sephton,
2009). Court and Sephton (2009) used pyrolysis to simulate
the ablation and pyrolysis of carbonaceous micrometeorites
upon atmospheric entry and showed that this process pro-
duces twice as much methane as the measured free methane
present in the CM2 carbonaceous chondrite, Murchison. This
source, however, produces less than 10 kg of methane an-
nually, a mass far below that required to maintain the
abundance of methane observed in the atmosphere of Mars.
5.2. The Phoenix lander and the detection
In the late northern spring, the Phoenix lander touched
down on Mars on May 25, 2008, inside the arctic circle at
68.228N, 234.258E, on a valley ﬂoor covered by the Scandia
Formation, a deposit that surrounds the northern margin of a
shield volcano named Alba Patera (Smith et al., 2009). The
main goal of Phoenix was to verify the presence of subsur-
face water ice (Smith et al., 2008). With regard to the search
for organics on Mars, the most important instrument on
Phoenix was the Thermal and Evolved Gas Analyzer (TEGA)
instrument. TEGA consists of a Thermal Analyzer containing
eight separate sample ovens, and a mass spectrometer with a
mass range of 2–140 dalton, called the Evolved Gas Analyzer
(Boynton et al., 2001). Five samples and two blanks were
analyzed by TEGA during the Phoenix mission (Arvidson
et al., 2009). The most interesting constituents found in these
samples were CaCO
(Boynton et al., 2009), H
O (Smith et al.,
2009), and O
(Hecht et al., 2009). TEGA did not detect any
organic material (Ming et al., 2009; Sutter et al., 2009). A
second instrument on the Phoenix lander was the Wet
Chemistry Laboratory (Hecht et al., 2008; Kounaves et al.,
2009), which was designed to add water and speciﬁed salts
to a sample of the martian soil and then measure the sam-
ple’s dissolved ionic components and properties; its chemical
and mineralogical composition, including sulfates; and its
acidity, metal content, and redox pairs (Smith et al., 2008).
One of the most interesting ﬁnds of the Wet Chemistry Lab-
oratory was the detection of perchlorates (ClO
4) in the
martian soil, at least some of which were in the form of
ORGANICS ON MARS? 593
Table 2. Laboratory Simulations on Organics on Mars
Atmospheric composition (%) Solar radiation
Temperature (8C) Pressure
He (nm) Light source
addition Oxides Reference
1979 Adenine, glycine,
Quartz tubes 10 to 25
0.001 - 100 - - - 200–300 Mercury-
- - Oro
1979 Olivine Pyroxene Mars
22 to 0 1000
- - - - 100 - - <67.8 mbar (to
et al., 1979
Pyrex ﬂasks R.T.
3.4 - - - 100 - UV-visible
- - Pang et al., 1982
1997 Palagonite Glycine Mars Jars R.T. 100 95.59 - 4.21 0.11 - 210–710 Xenon - - Stoker and
23 to þ10
------ - - H
et al., 1998
2000 Labradorite 30 6 Mars gas
254 (peak) Mercury - - Yen et al., 2000
- - - 100 -
2005 Glycine D-alanine Mars
- - - - - 190–325 Deuterium - - ten Kate et al.,
2006 Glycine D-alanine Mars
63 and R.T. 10
and 7 99.9 - - - - 190–325 Deuterium - - ten Kate et al.,
2006 Salten Skov
- - - - - 190–325 Deuterium - - Garry et al.,
63 7 99.9
2006 Amino acids Pyrex glass
- 100 - - - 0.50–
Co - - Kminek and
2008 ATP Mars
7.1 Mars gas
200–280 Xenon-arc - - Schuerger
et al., 2008
2009 Brines with amino
acids, with and
135 to þ40 7–15 95.3 2.7 1.6 0.13 - 250–700 Xenon-arc In suspension - Johnson and
2009 Aqueous solutions
of organics on
R.T. 196 1,000
air 355 Nd:YAG
laser (6 ns)
In suspension Goethite,
Glass jar 65 10
- - - - - 190–250 Xenon-arc - - Stalport et al.,
10 R.T. 6.9 95.5 2.7 1.6 0.13 - 200–280
- Hintze et al.,
100 355 Nd:YAG
et al., 2010
Adapted from Jensen et al., 2008.
Ambient terrestrial atmospheric pressure.
R.T. ¼room temperature *208C.
Applied doses: 0.50, 1.00, 2.05, 5.42 MGy.
(Hecht et al., 2009). These ﬁndings
were further endorsed by the detection of O
which evolved at temperature ranges consistent with the
thermal decomposition of perchlorates (Hecht et al., 2009).
This perchlorate ﬁnding is particularly interesting because,
although perchlorate does not readily oxidize organics under
martian conditions, the low water activity associated with
such a strongly desiccating substance may inhibit many
forms of life. The high-temperature oxidizing properties of
perchlorate will, however, promote combustion of organics
in pyrolytic experiments (Hecht et al., 2009), which could
have affected the ability of both Phoenix’s TEGA experiment
and the Viking mass spectrometer experiments to detect or-
ganics (Biemann, 2007; Ming et al., 2009).
6. The Suitability of Thermal Volatilization
Gas Chromatography–Mass Spectrometry
for the Detection of Organics on Mars
After the results from the Viking mission were analyzed
and did not directly show the presence of organics or life on
the surface of Mars, a debate ensued as to whether the in-
struments on Viking were the best choice for ﬁnding or-
ganics on Mars, either from an instrument sensitivity point of
view or a technique point of view. Biemann (1979) stated the
following: ‘‘First, the question arises, whether the instru-
ments indeed worked properly. Fortunately, experimental
data exists which demonstrates this proper function beyond
any doubt.’’ However, he also added that
certain types of organic material can not be detected
by the molecular analysis (thermal volatilization GCMS)
experiment, which consisted of heating the sample to
5008C in several steps followed by the analysis of organic
compounds evolved by volatilization or pyrolysis. Any
compound that would be stable at 5008C such as highly
cross-linked polymers, would probably not produce de-
tectable material. Compounds of the opposite behavior,
namely one that decomposes upon heating into certain
molecules, which the Viking GCMS can not detect, would
also remain unnoticed (Biemann, 1979).
Benner et al. (2000) suggested that organic compounds that
arrive on Mars through meteoritic delivery, such as alkanes,
alkylbenzenes, naphthalene and higher polycyclic aromatic
hydrocarbons, kerogen, and amino acids and hydroxyacids,
are most likely to be converted to carboxylic acid derivatives.
These compounds would not be easily detected by thermal
volatilization GCMS because they are either nonvolatile or
, CO, and H
O, which are present in the mar-
tian atmosphere and therefore difﬁcult to distinguish. At-
tempts to reproduce the Viking LR results led to conclusions
that the mechanism for the decomposition of organics in
Yungay soils is different from the processes observed in the
Viking LR experiment (Quinn et al., 2007) but also that a
mysterious oxidant in the martian soil that evolved oxygen
when humidiﬁed in the LR experiment might have been
of biological origin (Houtkooper and Schulze-Makuch,
2007). Viking GCMS-like experiment results (Navarro-
´lez et al., 2006) suggest that the presence of iron oxides
or their salts, or both, in other analyzed soil samples (e.g.,
jarosites from Rı
´o Tinto and Panoche Valley) caused the in-
trinsic organic material to oxidize to carbon dioxide (CO
which drastically attenuates the detection of organics. An-
other result from this study, which was that small amounts
of organics would fall below the detection limit of the Viking
GCMS, was refuted, however, because the equipment used
was a thousand times less sensitive than the Viking GCMS
and the experimental methods different from the Viking
methods (Biemann, 2007). In
˜iguez et al. (2009) further in-
vestigated the usefulness of thermal volatilization for organic
detection on Mars and found that there are two sources of
strong oxidizers in palagonite soils: hydroxyl radicals and
oxygen atoms. These strong oxidizers completely decom-
posed low levels of stearic and mellitic acids present in the
soil samples, which suggests that thermal volatilization
may not be the best method for organic detection on Mars.
´lez et al. (2009) showed that, when organics
are present in the soil at levels above 1500 ppm, several
characteristic organic fragments can be detected by thermal
volatilization mass spectrometry; however, when the levels
are below <150 ppm, thermal volatilization oxidizes them,
and no organic fragments are released. The most recent ex-
periments that have taken into account both Viking and
Phoenix data showed that, upon heating of Atacama soils
mixed with 1 wt% of magnesium perchlorate, all the organics
present were decomposed to water and carbon dioxide, but
that a small amount was chlorinated and formed chlor-
omethane and dichloromethane at 5008C (Navarro-Gonza
et al., 2010). ‘‘Re-interpretation of the Viking results therefore
suggests 0.1% perchlorates and 1.5–6.5 ppm organic carbon
at the landing site 1, and 0.1% perchlorates and 0.7–2.6 ppm
organic carbon at the landing site 2’’ (Navarro-Gonza
´lez et al.,
7. Laboratory Investigations of Organics on Mars
A few years after Viking, several processes were sug-
gested that could have led to the nondetection of organic
material. These processes can roughly be divided into four
categories: (i) the potential presence of some oxidizing agents
in the martian soil, (ii) the potential effects of electriﬁcation
and glow discharge, (iii) degradation by UV and other ra-
diation, and (iv) the photocatalytic effects caused by inter-
action of radiation with mineral surfaces. Table 2 shows an
overview of the studies performed that involve either one or
a combination of these effects.
The presence of an oxidizing source in the martian soil could
have destroyed organics. Klein (1979) suggested that a
thermally labile oxidant such as H
, which is known to
destroy organics, could have caused the evolution of CO
the LR experiments by reacting with the formate (CHOO
in the nutrient solution that was part of the experiment. This
could be produced due to photochemical reactions in
the martian atmosphere (Hunten, 1979) but also by frost
weathering (interaction of minerals with H
O frost) of olivine
(Huguenin et al., 1979; Huguenin, 1982). Oyama and Berdahl
(1979) determined that g-Fe
, which has been suggested to
be present on the martian surface (Hargraves et al., 1976),
could both oxidize organics directly as well as catalyze oxi-
dation through H
. This could explain the slow CO
duction in the LR and GEx experiments and the CO
production in the LR experiment. Ponnamperuma et al.
596 TEN KATE
(1977) had earlier obtained similar results by showing
production upon adding Viking nutrient mixture to g-Fe
On the other hand, there were also arguments against H
Levin and Straat (1981) proposed that H
reacted also with
compounds in nutrients other than only formate, which
suggests that the H
hypothesis did not account for the
fact that only one compound in LR was oxidized to CO
Furthermore, they found that there should by at least 2 wt%
in the soil to reproduce the LR results. This was
considered to be doubtful because there was hardly any
detected in the atmosphere (Hanel and Maguire, 1980,
in Levin and Straat, 1981), and H
has a short lifetime
s) against UV destruction.
A different approach suggested that the GEx and LR re-
sults may have been caused not by oxidation of organics but
by the presence of clays, such as smectites, in the martian
soil. These clays may have absorbed compounds from the
atmosphere that were released in the GEx experiment, and
their catalytic surfaces may have helped in decomposing the
formate in the LR nutrient, which would have released
the atmosphere in the LR experiment (Banin and Rishpon,
1979; Banin and Margulies, 1983).
In 1994, Zent and McKay offered that in the most realistic
model the martian soil contains oxidants produced by het-
erogeneous chemical reactions with a photochemically pro-
duced atmospheric oxidant. However, most compounds
with the capacity to oxidize H
, as seen in the GEx
experiment, are thermally labile or unstable against reduc-
tion by atmospheric CO
, and the oxidants most often sug-
gested to explain the LR experiment, including H
expected to decompose rapidly under martian UV (Zent and
McKay, 1994). The interaction between absorbed H
and ferrous) iron, and H
leads to very efﬁcient radical
production through the (photo-)Fenton reaction (Spacek
et al., 1995; Southworth and Voelker, 2003; Mo
Zhang et al., 2005), although this mechanism still needs the
presence of H
. Other oxidizing mechanisms that are not
based on H
have been proposed as well. Oxygen radicals
2) can be formed by the interaction of UV with Mars-
analog minerals both at martian temperatures (308C) and
room temperature in the presence of oxygen, either in a
Mars-like mixture or as pure oxygen with a partial pressure
comparable to that of the oxygen in the martian atmosphere
(Yen et al., 2000). In Mars analog environments on Earth, for
example, the Atacama Desert, dry acids can be produced
photochemically in the atmosphere from SO
cursors, which then adsorb onto dust and soil surfaces. High
relative humidity at night can then trigger oxidative acid soil
reactions. These soil acids are expected to play a signiﬁcant
role in the oxidizing nature of the soils, the formation of
mineral surface coatings, and the chemical modiﬁcation of
organics in the surface material (Quinn et al., 2005). Garry
et al. (2006) reached a similar conclusion based on experi-
ments that showed a decrease in intrinsic amino acid content
of cold martian soil analogues (608C) upon UV irradiation
in a CO
atmosphere with trace amounts of residual water.
In contrast, experiments (Mancinelli, 1989; McDonald et al.,
1998) have shown that an extract of terrestrial soil organics as
well as organic macromolecules, such as tholins and humic
acid, subjected to a H
O solution do not decrease
measurably, either at 208C or at low temperatures (588C
and 1238C), and might be stable against oxidation on the
martian surface, at least in the polar regions, over the entire
history of Mars.
7.2. Glow discharge
A second mechanism for organic degradation could be the
formation of electrostatically generated glow discharge plasmas
in martian dust storms, which could alter the local atmo-
spheric chemistry on Mars to produce reactive species, such
as hydrogen peroxide, and breakdown species, such as or-
ganic compounds (Mills, 1977; Oyama and Berdahl, 1979). In
Earth’s atmosphere, anhydrous electrical currents are gen-
erated in dust devils and dust storms (Freier, 1960; Crozier,
1964; Ette, 1971). In terrestrial dust devils, dust particles
generate and transfer electric charge through collisions with
each other and with the surface (Ette, 1971; Eden and Von-
negut, 1973; Farrell et al., 2003). In this process, smaller
particles get charged negatively and are eddied up in dust
storms, whereas larger grains become positively charged and
stay close to the surface (Ette, 1971; Gierasch and Goody,
1973; Melnik and Parrot, 1998; Farrell et al., 2003; Krauss
et al., 2003). This displacement in grain charge types creates a
dust storm–sized electric dipole moment, which results in
the development of coherently varying electric ﬁelds that
extend well outside the dust storm. Field strengths near
500 V m
at a distance of many 10s of meters from the
features have been measured (Freier, 1960; Crozier, 1964). In
desert tests that combined electrical, magnetic, and meteo-
rological measurements, electric ﬁelds were found to be co-
herent, and large scale, and to exceed 20 kV m
et al., 2004; Renno et al., 2004). Unsaturated electric ﬁelds near
120 kV m
were measured from dust devils in the Mojave
Desert ( Jackson and Farrell, 2006), and simple saltating
grains were found to generate electric ﬁelds exceeding
160 kV m
(Schmidt et al., 1998). These coherent electric
ﬁelds from dust devils are not impulsive ‘‘discharge ﬁelds’’
or lightning, but long-lasting electrostatic ﬁelds associated
with the buildup of vertical, well-separated charge centers in
the feature. Discharges occur when these electrostatic ﬁelds
become anomalously large, which creates ‘‘breakdown’’
conditions and leads to increased impulsive electron ﬂow.
It is anticipated, with Earth as an analogy, that martian
dust storms are also electrical in nature, as long as (1) vertical
winds exist to mass stratify grains and (2) the lifted grains
vary in size and composition [required for efﬁcient grain-
grain charge generation (Desch and Cuzzi, 2000)]. Both re-
quired conditions exist with the easily lifted iron mineral/
basalt grain mix on Mars. Melnik and Parrot (1998) modeled
these electrical processes in dust storms and found that the
macroscopic electrostatic ﬁelds within a martian dust cloud
could reach breakdown levels of *20 kV m
. The analytical
model of Farrell et al. (2003) compared the development of a
terrestrial and a martian dust storm of similar sizes and
found that both would ultimately develop comparable elec-
tric ﬁeld strengths (>20 kV m
), with the martian storm’s
temporal development about 15% slower due to current
leakage into the more conductive martian atmosphere.
Modeling has suggested that this dust-induced electro-
chemistry can signiﬁcantly increase the destruction rate of
methane, both via direct dissociation and the enhanced
production of OH- and H- (Farrell et al., 2006). Furthermore,
ORGANICS ON MARS? 597
Delory et al. (2006) found that under near-breakdown con-
ditions the dissociation of H
O via electron collisions pro-
duces negative ions (OH- and H-) at much higher rates than
photochemical processes, which will lead to a *200 times
larger subsequent production of H
(Atreya et al., 2006).
Within this context, Hintze et al. (2010) subjected ﬁve organic
compounds—phenanthrene, octadecane, octadecanoic acid,
decanophenone, and benzoic acid—to a glow discharge
plasma in a simulated martian atmosphere. The plasma
contained cations and excited neutral species, including
carbon dioxide, carbon monoxide, and nitrogen. After ex-
posure to the plasma, oxidized, higher-molecular-weight
versions of the parent compounds containing carbonyl, hy-
droxyl, and alkenyl functional groups were identiﬁed.
7.3. UV degradation
The third proposed organic destruction mechanism fo-
cuses on the relatively high UV ﬂux into short wavelength
ranges (190–400 nm, compared to 290–400 nm on the Earth’s
surface) that may efﬁciently destroy organic compounds.
´and Holzer (1979) exposed adenine, glycine, naphtha-
lene, and the Murchison meteorite to UV in the presence of
varying amounts of oxygen and measured their decompo-
sition. Adenine and glycine were found to be more stable
than naphthalene, and the degradation rates increased with
the amount of oxygen present. Another mechanism could
be titanium oxide–catalyzed photooxidation, where the or-
ganics are oxidized through interaction with a combination
of UV radiation, gaseous oxygen (present at 0.13% in the
martian atmosphere), and a catalyzing surface, such as TiO
which is also present on Mars (Chun et al., 1978; Pang et al.,
1982). Stoker and Bullock (1997) UV irradiated samples in
which glycine was mixed with a Mars analogue (palagonite
from the Mauna Kea Volcano on Hawaii). They measured
the headspace gases over the samples during irradiation for
traces of methane, assuming that the destruction of one
glycine molecule produced one methane molecule. They
found destruction rates of 2.24 1.210
g of carbon m
per year when scaled to martian surface conditions and
concluded that the surface of Mars should be depleted of
organics, based on the annual inﬂux of organic material
(Flynn, 1996). Ten Kate et al. (2005, 2006) also studied the
effects of UV radiation on glycine as well as on alanine, in the
form of thin layers of the pure amino acids. They found as
well that glycine and alanine have a short lifetime on the
martian surface, with half-lives of 22 5 h for glycine and
31 h for alanine (*500 and *81 h, respectively, in the lab),
when extrapolated to martian surface conditions. Further-
more, they found that these rates slowed down by a factor of
*10 when the samples were cooled to an average Mars’
surface temperature of 608C. A similar approach was used
by Stalport et al. (2009), who irradiated cold (558C) thin
ﬁlms of mellitic, benzoic, and oxalic acids in vacuum. The
half-lives of benzoic and oxalic acid as observed in the lab are
0.8 0.2 and 1.8 0.5 h, respectively, which is considerably
shorter than that of the amino acids studied by ten Kate et al.
(2005, 2006). Mellitic acid, on the other hand, produces a UV
radiotolerant compound identiﬁed as benzenehexacarboxylic
). This result led the authors to
conclude that, in spite of the eventual presence of oxidation
processes and UV radiation on the martian surface, com-
pounds produced by photolysis of benzenecarboxylic acids
(such as mellitic acid) may have accumulated into the mar-
tian regolith (Stalport et al., 2009). This conclusion is in line
with predictions by Benner et al. (2000). Schuerger et al.
(2008) studied the response of thin ﬁlms of adenosine tri-
phosphate (ATP), a molecule essential for life, to UV irradi-
ation in a Mars-like atmosphere. They found a half-life for
ATP of *4 days in the lab, which corresponds to *22 sols
(&22.6 Earth days) when extrapolated to martian surface
conditions. In the same facility, Hintze et al. (2010) exposed
the same ﬁve organic compounds as used in their glow
discharge experiments—phenanthrene, octadecane, octade-
canoic acid, decanophenone, and benzoic acid—to Mars-like
UV radiation in a simulated martian environment. The
UV degradation reactions also produced oxidized, higher-
molecular-weight compounds as compared to the starting
materials; however, this process seemed to be less efﬁcient
than glow discharge.
Besides UV, other ranges of the solar spectrum could af-
fect the martian surface as well. UV radiation will penetrate
only a few microns into the martian surface, which implies
that organics are safe from UV radiation when buried under
even a thin layer of soil (e.g., ten Kate et al., 2005). However,
cosmic rays will produce a higher dose-rate than they pro-
duce on Earth, since the martian atmospheric column density
at normal incidence is only 16–27 g cm
Earth’s atmospheric shield of 1000 g cm
, which is equiva-
lent to a depth of 9 m below ground on Mars (Clark, 1979).
Other studies have suggested that inﬂuence of galactic cos-
mic rays and solar energetic particles reaches much deeper
(several meters), compared to UV (Pavlov et al., 2002; Dart-
nell et al., 2007a, 2007b). Laboratory experiments in which
amino acids were irradiated with grays indicated that amino
acids buried in the ﬁrst meter of the martian subsurface
would be destroyed through radiolysis. Below a radiation
shielding depth of 400–500 g cm
, amino acids would not be
degraded substantially (Kminek and Bada, 2006).
7.4. The interaction of UV with organics absorbed
Recent studies have not only focused on the effect of UV
by itself but also on the catalytic effects mineral surfaces
could have on the interaction of UV with organic matter, a
process already suggested by Chun et al. (1978) and Pang
et al. (1982). Apart from radiolytic oxidation, racemization
[the process in which one enantiomer of an amino acid
converts to the other, e.g., L-alanine to D-alanine, until a 1:1
mixture is reached (Johnson and Pratt, 2010)] has been pro-
posed. Experiments involving ﬁve amino acids indicated that
the rates of racemization in the presence of metals in solution
are an order of magnitude slower than degradation through
radiolytic oxidation, and both are several orders of magni-
tude faster than previously reported by Bada and Schroeder
(1975), Snider and Wolfenden (2000), and Li and Brill
(2003). Shkrob and Chemerisov (2009) studied UV (355 nm)–
induced reactions of carboxylic, hydroxycarboxylic, and
aminocarboxylic acids, carboxylated aromatics, and R-amino
acids and peptides adsorbed on the hydrated metal oxides
), goethite (R-FeOOH), and hematite (R-Fe
598 TEN KATE
at low (196 to 738C) and room (228C) temperature. The
UV wavelength of 355 nm was chosen because at this
wavelength the light is completely absorbed by the oxides
and no direct photolysis of the organics takes place. They
showed that the main photodegradation path in these ex-
periments is decarboxylation catalyzed by the metal oxides.
This photocatalytic decarboxylation is inconsistent with the
Benner et al. (2000) hypothesis that chemical evolution of the
organic component of the soil results in the accumulation of
stable, nonvolatile carboxylated and polycarboxylated mol-
ecules in martian soil. This led the authors to suggest that
there may be no ‘‘safe haven’’ for organics on Mars. Further
analysis of these experiments, however, indicated that
during the process of photocatalytic decarboxylation both
form via the photo-Kolbe reaction (Shkrob et
al., 2010). In the sequence of processes suggested in this
work, the ultimate end product of organics delivered by
meteorites on the martian surface is CH
. Therefore, these
reactions may account for seasonally variable methane
production (Shkrob et al., 2010).
After 45 years of research on organic matter on the surface
of Mars, which included two missions that could have de-
tected organics, Viking and Phoenix, it is still unclear as
to whether organic matter is present on Mars. Work by
´lez et al. (2006, 2009, 2010) suggested that
thermal volatilization gas chromatography–mass spectrom-
etry, the method used on both missions, may not be the best
method to look for trace amounts of organics, because or-
ganics can be destroyed upon heating in a pyrolysis unit.
Organic matter should be detectable by thermal volatiliza-
tion mass spectrometry (e.g., ten Kate et al., 2010). Very recent
work by Shkrob and Chemerisov (2009), and Shkrob et al.
(2010), suggested that active removal processes take place
that could explain the observation that the martian surface is
depleted of organics, as well as the production of the CH
detected in the martian atmosphere. The best way to deter-
mine whether there are organics on Mars would be to look
for them in situ. The upcoming Mars Science Laboratory
scheduled for launch in the fall of 2011 is equipped with the
Sample Analysis at Mars (SAM) instrument suite (Mahaffy,
2008). A primary focus of SAM will be the detection and
identiﬁcation of organic molecules by way of thermal vola-
tilization gas chromatography–mass spectrometry. To en-
hance organic detectability by the GCMS, some of SAM’s
sample cups are ﬁlled with derivatization agents that will
dissolve organics from the soil before pyrolysis and make
them more volatile (Mahaffy, 2008). Two derivatization
methods to be used both react with amines, acids, and al-
cohols. Moreover, one of the methods is more suitable for
free organics, such as amino acids (Buch et al., 2006), the
other for bonded macromolecules. The effects of perchlorates
on these derivatization steps are currently under investiga-
tion ( J.L. Eigenbrode, D.P. Glavin, personal communication).
Even after a successful Mars Science Laboratory, future
missions should incorporate instruments that enable organic
detection. For these future missions, other organic detection
techniques should therefore be considered as well [e.g.,
capillary electrophoresis (Skelley et al., 2005)].
The author would like to thank Chris McKay and Sherry
Cady for the invitation to write this review paper and for
their helpful reviewer comments. Furthermore, many thanks
to Michael Chesnes from the Goddard Library for his tre-
mendous help in providing essential articles on very short
ATP, adenosine triphosphate; GCMS, gas chromato-
graph–mass spectrometer; GEx, gas exchange; LR, labeled
release; PR, pyrolytic release; SAM, the Sample Analysis at
Mars; TEGA, Thermal and Evolved Gas Analyzer.
Anders, E. (1964) Origin, age, and composition of meteorites.
Space Sci. Rev. 3:583–714.
Anderson, D., Biemann, K., Orgel, L., Oro
´, J., Owen, T., Shul-
man, G., Toulmin, P., and Urey, H. (1972) Mass spectrometric
analysis of organic compounds, water and volatile constitu-
ents in the atmosphere and surface of Mars: the Viking Mars
lander. Icarus 16:111–138.
Arvidson, R.E. and the Phoenix Science Team. (2009) Geologic
setting and surface properties of the Mars Phoenix landing site
[abstract 1067]. In 40
Lunar and Planetary Science Conference
Abstracts, Lunar and Planetary Institute, Houston.
Atreya, S., Wong, A., Renno, N., Farrell, W., Delory, G., Sentman,
D., Cummer, S., Marshall, J., Rafkin, S., and Catling, D. (2006)
Oxidant enhancement in martian dust devils and storms: im-
plications for life and habitability. Astrobiology 6:439–450.
Atreya, S.K., Mahaffy, P.R., and Wong, A.S. (2007) Methane and
related trace species on Mars: origin, loss, implications for life,
and habitability. Planet. Space Sci. 55:358–369.
Bada, J.L. and Schroeder, R.A. (1975) Amino acid racemization
reactions and their geochemical implications. Naturwissen-
Ballou, E.V., Wood, P.C., Wydeven, T., Lehwalt, M.E., and
Mack, R.E. (1978) Chemical interpretation of Viking Lander 1
life detection experiment. Nature 271:644–645.
Banin, A. and Margulies, L. (1983) Simulation of Viking biology
experiments suggests smectites not palagonites, as martian
soil analog. Nature 305:523–525.
Banin, A. and Rishpon, J. (1979) Smectite clays in Mars soil—
evidence for their presence and role in Viking biology exper-
imental results. J. Mol. Evol. 14:133–152.
Barker, E.S. (1972) Detection of molecular oxygen in the martian
atmosphere. Nature 238:447–448.
Benner, S.A., Devine, K.G., Matveeva, L.N., and Powell, D.H.
(2000) The missing organic molecules on Mars. Proc. Natl.
Acad. Sci. U.S.A. 97:2425–2430.
Biemann, K. (1979) The implications and limitations of the
ﬁndings of the Viking organic analysis experiment. J. Mol.
Biemann, K. (2007) On the ability of the Viking gas chromato-
graph–mass spectrometer to detect organic matter. Proc. Natl.
Acad. Sci. U.S.A. 104:10310–10313.
Biemann, K., Oro
´, J., Toulmin, P., III, Orgel, L., Nier, A., An-
derson, D., Simmonds, P., Flory, D., Diaz, A., and Rushneck,
D. (1976) Search for organic and volatile inorganic compounds
in two surface samples from the Chryse Planitia region of
Mars. Science 194:72–76.
ORGANICS ON MARS? 599
Biemann, K., Oro
´, J., Toulmin, P., III, Orgel, L.E., Nier, A.O.,
Anderson, D.M., Simmonds, P.G., Flory, D., Diaz, A.V.,
Rushneck, D.R., Biller, J.E., and Laﬂeur, A.L. (1977) The search
for organic substances and inorganic volatile compounds in
the surface of Mars. J. Geophys. Res. 82:4641–4658.
Bland, P.A. and Smith, T.B. (2000) Meteorite accumulations on
Mars. Icarus 144:21–26.
Botta, O. and Bada, J.L. (2002) Extraterrestrial organic com-
pounds in meteorites. Surveys in Geophysics 23:411–467.
Boynton, W., Ming, D., Kounaves, S., Young, S., Arvidson, R.,
Hecht, M., Hoffman, J., Niles, P., Hamara, D., and Quinn, R.
(2009) Evidence for calcium carbonate at the Mars Phoenix
landing site. Science 325:61–64.
Boynton, W.V., Bailey, S.H., Hamara, D.K., Williams, M.S.,
Bode, R.C., Fitzgibbon, M.R., Ko, W.J., Ward, M.G., Sridhar,
K.R., Blanchard, J.A., Lorenz, R.D., May, R.D., Paige, D.A.,
Pathare, A.V., Kring, D.A., Leshin, L.A., Ming, D.W., Zent,
A.P., Golden, D.C., Kerry, K.E., Lauer, H.V., and Quinn, R.C.
(2001) Thermal and evolved gas analyzer: part of the Mars
Volatile and Climate Surveyor integrated payload. J. Geophys.
Buch, A., Glavin, D.P., Sternberg, R., Szopa, C., Rodier, C.,
´lez, R., Raulin, F., Cabane, M., and Mahaffy,
P.R. (2006) A new extraction technique for in situ analyses of
amino and carboxylic acids on Mars by gas chromatography
mass spectrometry. Planet. Space Sci. 54:1592–1599.
Christensen, P.R., Bandﬁeld, J., Bellm, J.F., Gorelick, N., Ha-
milton, V.E., Ivanov, A., Jakosky, B.M., Kieffer, H.H., Lane,
M.D., Jakosky, B.M., Kieffer, H.H., Lane, M.D., Malin, M.C.,
McConnochie, T.H., McEwen, A.S., McSween, H.Y., Mehall,
G.L., Moersch, J.E., Nealson, K.H., Rice, J.W., Richardson,
M.I., Ruff, S.W., Smith, M.D., Titus, T.N., and Wyatt. M.B.
(2003) Morphology and composition of the surface of Mars:
Mars Odyssey THEMIS results. Science 300:2056–2061.
Christensen, P.R., McSween, H.Y., Bandﬁeld, J.L., Ruff, S.W.,
Rogers A.D., Gorelick, N., Wyatt. M.B., Jakosky, B.M., Kieffer,
H.H., Mailin, M.C., and Moersch, J.E. (2005) Evidence for
magmatic evolution and diversity on Mars from infared ob-
servations. Nature 436:2056–2061.
Chun, S., Pang, K., Cutts, J., and Ajello, J. (1978) Photocatalytic
oxidation of organic compounds on Mars. Nature 274:875–
Chyba, C. and Sagan, C. (1992) Endogenous production, ex-
ogenous delivery and impact-shock synthesis of organic
molecules: an inventory for the origins of life. Nature 355:
Clark, B.C. (1979) Chemical and physical microenvironments at
the Viking landing sites. J. Mol. Evol. 14:13–31.
Court,R.W.andSephton,M.A.(2009) Investigating the con-
tribution of methane produced by ablating micrometeorites
to the atmosphere of Mars. Earth Planet. Sci. Lett. 288:382–
Crovisier, J. (2004) The molecular complexity of comets. In Astro-
biology: Future Perspectives, edited by P. Ehrenfreund, W.
Irvine, T. Owen, L. Becker, J. Blank, J. Brucato, L. Colangeli, S.
Derenne, A. Dutrey, D. Despois, A. Lazcano, and F. Robert,
Kluwer Academic Publishers, Dordrecht, the Netherlands, pp
Crozier, W. (1964) Electric ﬁeld of New Mexico dust devil. J.
Geophys. Res. 69:5427–5429.
Dartnell, L.R., Desorgher, L., Ward, J.M., and Coates, A.J.
(2007a) Modelling the surface and subsurface martian radia-
tion environment: implications for astrobiology. Geophys. Res.
Lett. 34, doi:10.1029/2006GL027494.
Dartnell, L.R., Desorgher, L., Ward, J.M., and Coates, A.J.
(2007b) Martian sub-surface ionising radiation: biosignatures
and geology. Biogeosciences 4:545–588.
Delory, G., Farrell, W., Atreya, S., Renno, N., Wong, A., Cum-
mer, S., Sentman, D., Marshall, J., Rafkin, S., and Catling, D.
(2006) Oxidant enhancement in martian dust devils and
storms: storm electric ﬁelds and electron dissociative attach-
ment. Astrobiology 6:451–462.
Desch, S. and Cuzzi, J. (2000) The generation of lightning in the
solar nebula. Icarus 143:87–105.
Dycus, R.D. (1969) The meteorite ﬂux at the surface of Mars.
Publ. Astron. Soc. Pac. 81:399–414.
Eden, H.F. and Vonnegut, B. (1973) Electrical breakdown caused
by dust motion in low-pressure atmospheres: considerations
for Mars. Science 180:962–963.
Ehrenfreund, P. and Charnley, S.B. (2000) Organic molecules in
the interstellar medium, comets, and meteorites: a voyage
from dark clouds to the early Earth. Annu. Rev. Astron. Astro-
Ette, A. (1971) The effect of the harmattan dust on atmospheric
electric parameters. Journal of Atmospheric and Terrestrial Phy-
Fanale, F.P. (1971) History of martian volatiles: implications for
organic synthesis. Icarus 15:279–303.
Farrell, W., Delory, G., Cummer, S., and Marshall, J. (2003) A
simple electrodynamic model of a dust devil. Geophys. Res.
Farrell, W., Smith, P., Delory, G., Hillard, G., Marshall, J., Ca-
tling, D., Hecht, M., Tratt, D., Renno, N., Desch, M., Cummer,
S., Houser, J., and Johnson, B. (2004) Electric and magnetic
signatures of dust devils from the 2000–2001 MATADOR
desert tests. J. Geophys. Res. 109, doi:10.1029/2003JE002088.
Farrell, W., Delory, G., and Atreya, S. (2006) Martian dust storms
as a possible sink of atmospheric methane. Geophys. Res. Lett.
Flynn, G.J. (1996) The delivery of organic matter from asteroids
and comets to the early surface of Mars. Earth Moon Planets
Flynn, G.J. and McKay, D.S. (1990) An assessment of the mete-
oritic contribution to the martian soil. J. Geophys. Res. 95:
Formisano, V., Atreya, S., Encrenaz, T., Ignatiev, N., and Giur-
anna, M. (2004) Detection of methane in the atmosphere of
Mars. Science 306:1758–1761.
Freier, G. (1960) The electric ﬁeld of a large dust devil. J. Geophys.
Garry, J.R.C., Ten Kate, I.L., Martins, Z., Nornberg, P., and
Ehrenfreund, P. (2006) Analysis and survival of amino ac-
ids in martian regolith analogs. Meteorit. Planet. Sci. 41:391–
Geminale, A., Formisano, V., and Giuranna, M. (2008) Methane
in martian atmosphere: average spatial, diurnal, and seasonal
behaviour. Planet. Space Sci. 56:1194–1203.
Gierasch, P. and Goody, R. (1973) A model of a martian great
dust storm. Journal of the Atmospheric Sciences 30:169–179.
Hargraves, R.B., Collinson, D.W., and Spitzer, C.R. (1976) Viking
magnetic properties investigation: preliminary results. Science
Hecht, M.H., Marshall, J., Pike, W., Staufer, U., Blaney, D.,
Braendlin, D., Gautsch, S., Goetz, W., Hidber, H., Keller, H.U.,
Markiewicz, W.J., Mazer, A., Meloy, T., Morookian, J., Mo-
gensen, C., Parrat, D., Smith, P., Sykulska, H., Tanner, R.,
Reynolds, R., Tonin, A., Vijendran, S., Weilert, M., and Woida,
P. (2008) Microscopy capabilities of the Microscopy, Electro-
600 TEN KATE
chemistry, and Conductivity Analyzer. J. Geophys. Res. 113,
Hecht, M.H., Kounaves, S.P., Quinn, R.C., West, S.J., Young,
S.M.M., Ming, D.W., Catling, D.C., Clark, B.C., Boynton,
W.V., Hoffman, J., DeFlores, L.P., Gospodinova, K., Kapit, J.,
and Smith, P.H. (2009) Detection of perchlorate and the sol-
uble chemistry of martian soil at the Phoenix lander site. Sci-
Hintze, P., Buhler, C., Schuerger, A., and Calle, L. (2010) Al-
teration of ﬁve organic compounds by glow discharge plasma
and UV light under simulated Mars conditions. Icarus
Horowitz, N., Hubbard, J.S., and Hobby, G.L. (1972) The carbon-
assimilation experiment: the Viking Mars lander. Icarus
Horowitz, N.H., Hobby, G.L., and Hubbard, J.S. (1976) The Vi-
king carbon assimilation experiments—interim report. Science
Horowitz, N.H., Hobby, G.L., and Hubbard, J.S. (1977) Viking
on Mars—the carbon assimilation experiments. J. Geophys. Res.
Houtkooper, J. and Schulze-Makuch, D. (2007) A possible bio-
genic origin for hydrogen peroxide on Mars: the Viking results
reinterpreted. Int. J. Astrobiology 6:147–152.
Hubbard, J., Hardy, J., Voecks, G., and Golub, E. (1973) Photo-
catalytic synthesis of organic compounds from CO and water:
involvement of surfaces in the formation and stabilization of
products. J. Mol. Evol. 2:149–166.
Hubbard, J.S. (1976) The pyrolytic release experiment: mea-
surement of carbon assimilation. Orig. Life 7:281–292.
Hubbard, J.S., Hardy, J.P., and Horowitz, N.H. (1971) Photo-
catalytic production of organic compounds from CO and H
in a simulated martian atmosphere. Proc. Natl. Acad. Sci.
Huguenin,R.L.(1982)Chemical weathering and the Viking
biology experiments on Mars. J. Geophys. Res. 87:10069–
Huguenin, R.L., Miller, K.J., and Harwood, W.S. (1979) Frost-
weathering on Mars—experimental evidence for peroxide
formation. J. Mol. Evol. 14:103–132.
Hunten, D.M. (1979) Possible oxidant sources in the atmosphere
and surface of Mars. J. Mol. Evol. 14:71–78.
˜iguez, E., Navarro-Gonza
´lez, R., de la Rosa, J., Uren
F., Coll, P., Raulin, F., and McKay, C.P. (2009) On the oxida-
tion ability of the NASA Mars-1 soil simulant during
the thermal volatilization step: implications for the search of
organics on Mars. Geophys. Res. Lett. 36, doi:10.1029/
Jackson, T. and Farrell, W. (2006) Electrostatic ﬁelds in dust
devils: an analog to Mars. IEEE Trans. Geosci. Remote Sens.
Jensen, L.L., Merrison, J., Hansen, A.A., Mikkelsen, K.A., Kris-
toffersen, T., Nørnberg, P., Lomstein, B.A., and Finster, K.
(2008) A facility for long-term Mars simulation experiments:
the Mars Environmental Simulation Chamber (MESCH). Astro-
Johnson, A.P. and Pratt, L.M. (2010) Metal-catalyzed degrada-
tion and racemization of amino acids in iron sulfate brines
under simulated martian surface conditions. Icarus 207:
Klein, H., Horowitz, N., Levin, G., Oyama, V., Lederberg, J.,
Rich, A., Hubbard, J., Hobby, G., Straat, P., Berdahl, B., Carle,
G., Brown, F., and Johnson, R. (1976) Viking biological
investigation—preliminary results. Science 194:99–105.
Klein, H.P. (1974) Automated life-detection experiments for the
Viking mission to Mars. Orig. Life 5:431–441.
Klein, H.P. (1977) The Viking biological investigation: general
aspects. J. Geophys. Res. 82:4677–4680.
Klein, H.P. (1979) Simulation of the Viking biology experiments:
an overview. J. Mol. Evol. 14:161–165.
Kminek, G. and Bada, J.L. (2006) The effect of ionizing radiation
on the preservation of amino acids on Mars. Earth Planet. Sci.
Kounaves, S.P., Hecht, M.H., West, S.J., Morookian, J.M., Young,
S.M.M., Quinn, R., Grunthaner, P., Wen, X.W., Weilert, M.,
Cable, C.A., Fisher, A., Gospodinova, K., Kapit, J., Stroble, S.,
Hsu, P.C., Clark, B.C., Ming, D.W., and Smith, P.H. (2009) The
MECA wet chemistry laboratory on the 2007 Phoenix Mars
Scout lander. J. Geophys. Res. 114, doi:10.1029/2008JE003084.
Krasnopolsky, V., Maillard, J., and Owen, T. (2004) Detection of
methane in the martian atmosphere: evidence for life? Icarus
Krasnopolsky, V.A. (2005) A sensitive search for SO
martian atmosphere: implications for seepage and origin of
methane. Icarus 178:487–492.
Krauss, C.E., Hora
´nyi, M., and Robertson, S. (2003) Experi-
mental evidence for electrostatic discharging of dust near the
surface of Mars. New J. Phys. 5:70.71–70.79.
`vre, F. and Forget, F. (2009) Observed variations of methane
on Mars unexplained by known atmospheric chemistry and
physics. Nature 460:720–723.
Levin, G.V. (1972) Detection of metabolically produced labeled
gas: the Viking Mars lander. Icarus 16:153–166.
Levin, G.V. and Straat, P.A. (1976a) Labeled release—an exper-
iment in radiorespirometry. Orig. Life 7:293–311.
Levin, G.V. and Straat, P.A. (1976b) Viking labeled release
biology experiment—interim results. Science 194:1322–1329.
Levin, G.V. and Straat, P.A. (1977) Recent results from the Vi-
king labeled release experiment on Mars. J. Geophys. Res.
Levin, G.V. and Straat, P.A. (1979) Laboratory simulations of the
Viking labeled release experiment: kinetics following second
nutrient injection and the nature of the gaseous end product. J.
Mol. Evol. 14:185–197.
Levin, G.V. and Straat, P.A. (1981) A search for a nonbiological
explanation of the Viking labeled release life detection ex-
periment. Icarus 45:494–516.
Li, J. and Brill, T.B. (2003) Spectroscopy of hydrothermal reac-
tions, part 26: kinetics of decarboxylation of aliphatic amino
acids and comparison with the rates of racemization. Inter-
national Journal of Chemical Kinetics 35:602–610.
Mahaffy, P. (2008) Exploration of the habitability of Mars: de-
velopment of analytical protocols for measurement of organic
carbon on the 2009 Mars science laboratory. Space Sci. Rev.
Mancinelli, R.L. (1989) Peroxides and the survivability of mi-
croorganisms on the surface of Mars. Adv. Space Res. 9:191–
Marcus, A.H. (1968) Martian craters: number density. Science
Mariner Mars 1971 Science Experimenter Teams. (1973) Mariner
Mars 1971 Project Final Report: Science Results, Vol. 4, NASA
Technical Report 32-1550, National Aeronautics and Space
Administration, Washington DC.
McDonald, G.D., de Vanssay, E., and Buckley, J.R. (1998) Oxi-
dation of organic macromolecules by hydrogen peroxide:
implications for stability of biomarkers on Mars. Icarus 132:
ORGANICS ON MARS? 601
Melnik, O. and Parrot, M. (1998) Electrostatic discharge in
martian dust storms. J. Geophys. Res. 103:29107–29117.
Millar, T.J. (2004) Growth of large molecules and small grains. In
Astrobiology: Future Perspectives, edited by P. Ehrenfreund, W.
Irvine, T. Owen, L. Becker, J. Blank, J. Brucato, L. Colangeli, S.
Derenne, A. Dutrey, D. Despois, A. Lazcano, and F. Robert,
Kluwer Academic Publishers, Dordrecht, the Netherlands, pp
Mills, A.A. (1977) Dust clouds and frictional generation of glow
discharges on Mars. Nature 268:614.
Ming, D.W., Lauer, H.V., Archer, P.D., Sutter, B., Golden, D.C.,
Morris, R.V., Niles, P.B., and Boynton, W.V. (2009) Combus-
tion of organic molecules by the thermal decomposition of
perchlorate salts: implications for organics at the Mars Phoe-
nix Scout landing site [abstract 2241]. In 40
Lunar and Pla-
netary Science Conference Abstracts, Lunar and Planetary
¨hlmann, D.T.F. (2004) Water in the upper martian surface at
mid- and low-latitudes: presence, state, and consequences.
Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T.,
Bonev, B.P., DiSanti, M.A., Mandell, A.M., and Smith, M.D.
(2009) Strong release of methane on Mars in northern summer
2003. Science 323:1041–1045.
Nagy, B. (1975) Carbonaceous Meteorites, Elsevier Scientiﬁc Pub-
lishing, Amsterdam, pp 1–747.
´lez, R., Navarro, K.F., de la Rosa, J., In
Molina, P., Miranda, L.D., Morales, P., Cienfuegos, E., Coll, P.,
Raulin, F., Amils, R., and McKay, C.P. (2006) The limitations
on organic detection in Mars-like soils by thermal volatili-
zation-gas chromatography-MS and their implications for
the Viking results. Proc. Natl. Acad. Sci. U.S.A. 103:16089–
´lez, R., In
˜iguez, E., de la Rosa, J., and McKay,
C.P. (2009) Characterization of organics, microorganisms,
desert soils, and Mars-like soils by thermal volatilization
coupled to mass spectrometry and their implications for the
search for organics on Mars by Phoenix and future space
missions. Astrobiology 9:703–715.
´lez, R., Vargas, E., de la Rosa, J., Raga, A.C., and
McKay, C.P. (2010) Reanalysis of the Viking results suggests
perchlorate and organics at mid-latitudes on Mars. J. Geophys.
Res. in press.
Neukum, G., Jaumann, R., Hoffmann, H., Hauber, E., Head,
J.W., Basilevsky, A.T., Ivanov, B.A., Werner, S.C., van Gasselt,
S., Murray, J.B., McCord, T., and the HRSC Co-Investigator
Team. (2004) Recent and episodic volcanic and glacial activity
on Mars revealed by the High Resolution Stereo Camera.
´, J. (1972) Extraterrestrial organic analysis. Space Life Sci.
´, J. and Flory, D. (1973) Organic analysis of lunar samples
and the martian surface. Life Sci. Space Res. 11:43–54.
´, J. and Holzer, G. (1979) The photolytic degradation and
oxidation of organic compounds under simulated martian
conditions. J. Mol. Evol. 14:153–160.
Oyama, V., Berdahl, B., Carle, G., Lehwalt, M., and Ginoza, H.
(1976) Search for life on Mars—Viking 1976 gas changes as in-
dicators of biological-activity. Orig. Life Evol. Biosph. 7:313–333.
Oyama, V.I. (1972) The gas exchange experiment for life detec-
tion: the Viking Mars lander. Icarus 16:167–184.
Oyama, V.I. and Berdahl, B.J. (1977) The Viking gas exchange
experiment results from Chryse and Utopia surface samples. J.
Geophys. Res. 82:4669–4676.
Oyama, V.I. and Berdahl, B.J. (1979) A model of martian surface
chemistry. J. Mol. Evol. 14:199–210.
Oze, C. and Sharma, M. (2005) Have olivine, will gas: serpenti-
nization and the abiogenic production of methane on Mars.
Geophys. Res. Lett. 32, doi:10.1029/2005GL022691.
Palandri, J.L. and Reed, M.H. (2004) Geochemical models of
metasomatism in ultramaﬁc systems: serpentinization, ro-
dingitization, and sea ﬂoor carbonate chimney precipitation.
Geochim. Cosmochim. Acta 68:1115–1133.
Pang, K.D., Chun, S.F.S., Ajello, J.M., Nansheng, Z., and Minji, L.
(1982) Organic and inorganic interpretations of the martian
UV-IR reﬂectance spectrum. Nature 295:43–46.
Pavlov, A.K., Blinov, A.V., and Konstantinov, A.N. (2002) Ster-
ilization of martian surface by cosmic radiation. Planet. Space
Ponnamperuma, C., Shimoyama, A., Yamada, M., Hobo, T., and
Pal, R. (1977) Possible surface reactions on Mars: implications
for Viking biology results. Science 197:455–457.
Quinn, R.C., Zent, A.P., Grunthaner, F.J., Ehrenfreund, P., Tay-
lor, C.L., and Garry, J.R.C. (2005) Detection and character-
ization of oxidizing acids in the Atacama Desert using the
Mars oxidation instrument. Planet. Space Sci. 53:1376–1388.
Quinn, R.C., Ehrenfreund, P., Grunthaner, F.J., Taylor, C.L., and
Zent, A.P. (2007) Decomposition of aqueous organic com-
pounds in the Atacama Desert and in martian soils. J. Geophys.
Renno, N., Abreu, V., Koch, J., Smith, P., Hartogensis, O., De
Bruin, H., Burose, D., Delory, G., Farrell, W., Watts, C., Gar-
atuza, J., Parker, M., and Carswell, A. (2004) MATADOR 2002:
a pilot ﬁeld experiment on convective plumes and dust devils.
J. Geophys. Res. 109, doi:10.1029/2003JE002219.
Schmidt, D.S., Schmidt, R.A., and Dent, J.D. (1998) Electrostatic
force on saltating sand. J. Geophys. Res. 103:8997–9001.
Schuerger, A.C. and Clark, B.C. (2008) Viking biology experi-
ments: Lessons learned and the role of ecology in future Mars
life-detection experiments. Space Sci. Rev. 135:233–243.
Schuerger, A.C., Fajardo-Cavazos, P., Clausen, C.A., Moores,
J.E., Smith, P.H., and Nicholson, W.L. (2008) Slow degradation
of ATP in simulated martian environments suggests long
residence times for the biosignature molecule on spacecraft
surfaces on Mars. Icarus 194:86–100.
Sephton, M.A. (2002) Organic compounds in carbonaceous me-
teorites. National Product Report, the Royal Society of Chemistry
Shkrob, I.A. and Chemerisov, S.D. (2009) Light induced frag-
mentation of polyfunctional carboxylated compounds on hy-
drated metal oxide particles: from simple organic acids to
peptides. J. Phys. Chem. C. Nanomater Interfaces 113:17138–
Shkrob, I.A., Chemerisov, S.D., and Marin, T.W. (2010) Photo-
catalytic decomposition of carboxylated molecules on light-
exposed martian regolith and its relation to methane pro-
duction on Mars. Astrobiology 10:425–436.
Skelley, A.M., Scherer, J.R., Aubrey, A.D., Grover, W.H., Ivester,
R.H.C., Ehrenfreund, P., Grunthaner, F.J., Bada, J.L., and
Mathies, R.A. (2005) Development and evaluation of a mi-
crodevice for amino acid biomarker detection and analysis on
Mars. Proc. Natl. Acad. Sci. U.S.A. 102:1041–1046.
Smith, P.H., Tamppari, L., Arvidson, R.E., Bass, D., Blaney, D.,
Boynton, W., Carswell, A., Catling, D., Clark, B., Duck, T.,
DeJong, E., Fisher, D., Goetz, W., Gunnlaugsson, P., Hecht,
M., Hipkin, V., Hoffman, J., Hviid, S., Keller, H., Kounaves, S.,
Lange, C.F., Lemmon, M., Madsen, M., Malin, M., Markie-
wicz, W., Marshall, J., McKay, C., Mellon, M., Michelangeli,
602 TEN KATE
D., Ming, D., Morris, R., Renno, N., Pike, W.T., Staufer, U.,
Stoker, C., Taylor, P., Whiteway, J., Young, S., and Zent, A.
(2008) Introduction to special section on the Phoenix mission:
landing site characterization experiments, mission overviews,
and expected science. J. Geophys. Res. 113, doi:10.1029/
Smith, P.H., Tamppari, L.K., Arvidson, R.E., Bass, D., Blaney, D.,
Boynton, W.V., Carswell, A., Catling, D.C., Clark, B.C., Duck,
T., Dejong, E., Fisher, D., Goetz, W., Gunnlaugsson, H.P.,
Hecht, M.H., Hipkin, V., Hoffman, J., Hviid, S.F., Keller, H.U.,
Kounaves, S.P., Lange, C.F., Lemmon, M.T., Madsen, M.B.,
Markiewicz, W.J., Marshall, J., Mckay, C.P., Mellon, M.T.,
Ming, D.W., Morris, R.V., Pike, W.T., Renno, N., Staufer, U.,
Stoker, C., Taylor, P., Whiteway, J.A., and Zent, A.P. (2009)
O at the Phoenix landing site. Science 325:58–61.
Snider, M.J. and Wolfenden, R. (2000) The rate of spontaneous
decarboxylation of amino acids. J. Am. Chem. Soc. 122:11507–
Soffen, G.A. (1977) The Viking project. J. Geophys. Res. 82:3959–
Southworth, B.A. and Voelker, B.M. (2003) Hydroxyl radical
production via the photo-Fenton reaction in the presence of
fulvic acid. Environ. Sci. Technol. 37:1130–1136.
Spacek, W., Bauer, R., and Heisler, G. (1995) Heterogeneous and
homogeneous waste-water treatment comparison between
photodegradation with TiO
and the photo-Fenton reaction.
Stalport, F., Coll, P., Szopa, C., Cottin, H., and Raulin, F. (2009)
Investigating the photostability of carboxylic acids exposed to
Mars surface ultraviolet radiation conditions. Astrobiology
Stoker, C.R. and Bullock, M.A. (1997) Organic degradation under
simulated martian conditions. J. Geophys. Res. 102:10881–10888.
Sutter, B., Ming, D.W., Boynton, W.V., Niles, P.B., Hoffman, J.,
Lauer, H.V., and Golden, D.C. (2009) Summary of results from
the Mars Phoenix lander’s thermal evolved gas analyzer [ab-
stract 8004]. In The New Martian Chemistry Workshop, Lunar
and Planetary Institute, Houston.
ten Kate, I.L., Garry, J., Peeters, Z., Quinn, R., Foing, B., and
Ehrenfreund, P. (2005) Amino acid photostability on the
martian surface. Meteorit. Planet. Sci. 40:1185–1193.
ten Kate, I.L., Garry, J.R.C., Peeters, Z., Foing, B., and Ehren-
freund, P. (2006) The effects of martian near surface conditions
on the photochemistry of amino acids. Planet. Space Sci. 54:
ten Kate, I.L., Cardiff, E.H., Dworkin, J.P., Feng, S.H., Holmes,
V., Malespin, C., Stern, J., Swindle, T.D., and Glavin D.P.
(2010) VAPoR—Volatile Analysis by Pyrolysis of Regolith—
an instrument for in situ detection of water, noble gases, and
organics on the Moon. Planet. Space Sci. 58:1007–1017.
Tyson, B. and Oyama, V. (1973) Photoinduced ﬁxation of CO
amino acids: implications for nonbiological reactions on the
martian soil. Biosystems 5:98–102.
Werner, S.C. (2008) The early martian evolution—constraints
from basin formation ages. Icarus 195:45–60.
Wong, A., Atreya, S., and Encrenaz, T. (2003) Chemical markers
of possible hot spots on Mars. J. Geophys. Res. 108, doi:10.1029/
Yen, A., Kim, S., Hecht, M., Frant, M., and Murray, B. (2000)
Evidence that the reactivity of the martian soil is due to super-
oxide ions. Science 289:1909–1912.
Young, R.S., Ponnamperuma, C., and McCaw, B.K. (1965)
Abiogenic synthesis on Mars. Life Sci. Space Res. 3:127–
Zent, A.P. and McKay, C.P. (1994) The chemical reactivity of the
martian soil and implications for future missions. Icarus
Zhang, H., Choi, H.J., and Huang, C.P. (2005) Optimization of
Fenton process for the treatment of landﬁll leachate. J. Hazard.
Address correspondence to:
Inge L. ten Kate
NASA Goddard Space Flight Center
Greenbelt, MD 20771
Submitted 7 May 2010
Accepted 29 May 2010
ORGANICS ON MARS? 603