Penelope J. Boston's research while affiliated with NASA Johnson Space Center and other places

Publications (145)

Preprint
Viruses are the most numerically abundant biological entities on Earth. As ubiquitous replicators of information molecules and agents of community change, viruses have potent effects on life on Earth and may play a critical role in human spaceflight missions, life detection missions to other planetary bodies, and in planetary protection. However, m...
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Nearly half a century ago, two papers postulated the likelihood of lunar lava tube caves using mathematical models. Today, armed with an array of orbiting and fly-by satellites and survey instrumentation, we have now acquired cave data across our solar system—including the identification of potential cave entrances on the Moon, Mars, and at least n...
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Recent observations have shown the atmospheric greenhouse gas methane (CH 4 ) is consumed by microorganisms (methanotrophs) in caves at rates comparable to CH 4 oxidation in surface soils. Caves are abundant in karst landscapes that comprise 14% of Earth’s land surface area, and therefore may represent a potentially important, but overlooked, CH 4...
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Lava caves, tubes, and fumaroles in Hawai'i present a range of volcanic, oligotrophic environments from different lava flows and host unexpectedly high levels of bacterial diversity. These features provide an opportunity to study the ecological drivers that structure bacterial community diversity and assemblies in volcanic ecosystems and compare th...
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The 15th UN Convention on Biological Diversity (CBD) (COP15) will be held in Kunming, China in October 2021. Historically, CBDs and other multilateral treaties have either alluded to or entirely overlooked the subterranean biome. A multilateral effort to robustly examine, monitor, and incorporate the subterranean biome into future conservation targ...
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The 15th UN Convention on Biological Diversity (CBD) (COP15) will be held in Kunming, China in October 2021. Historically, CBDs and other multilateral treaties have either alluded to or entirely overlooked the subterranean biome. A multilateral effort to robustly examine, monitor, and incorporate the subterranean biome into future conservation targ...
Preprint
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Martian subsurface habitability and astrobiology can be evaluated via a lava tube cave, without drilling. MACIE addresses two key goals of the Decadal Survey (2013-2022) and three MEPAG goals. New advances in robotic architectures, autonomous navigation, target sample selection, and analysis will enable MACIE to explore the Martian subsurface.
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Ancient Venus and Earth may have been similar in crucial ways for the development of life, such as liquid water oceans, land-ocean interfaces, favorable chemical ingredients, and energy pathways. If life ever developed on, or was transported to, early Venus from elsewhere, it might have thrived, expanded, and then survived the changes that have led...
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Biovermiculations are uniquely patterned organic rich sediment formations found on the walls of caves and other subterranean environments. These distinctive worm-like features are the combined result of physical and biological processes. The diverse microbial communities that inhabit biovermiculations may corrode the host rock, form secondary miner...
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Terrestrial caves offer scientific and engineering insights and serve as testing grounds for future forays by humans and robots into caves on other worlds. https://eos.org/science-updates/planetary-cave-exploration-progresses
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A prototype rover carrying an astrobiology payload was developed and deployed at analog field sites to mature generalized system architectures capable of searching for biosignatures in extreme terrain across the Solar System. Specifically, the four-legged Limbed Excursion Mechanical Utility Robot (LEMUR) 3 climbing robot with microspine grippers ca...
Conference Paper
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All spacecraft sent to the Moon carry viable microorganisms with them. Historical measurements and recent mathematical models predict that even after the effect of space exposure and, in some cases, high-velocity impact, most deliver a bioburden of thousands to millions of cells each to the Moon. While it is widely assumed that no life can withstan...
Preprint
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Ancient Venus and Earth may have been similar in crucial ways for the development of life, such as liquid water oceans, land-ocean interfaces, the favorable chemical ingredients and energy pathways. If life ever developed on, or was transported to, early Venus from elsewhere, it might have thrived, expanded and survived the changes that have led an...
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On November 5-8, 2019, the "Mars Extant Life: What's Next?" conference was convened in Carlsbad, New Mexico. The conference gathered a community of actively publishing experts in disciplines related to habitability and astrobiology. Primary conclusions are as follows: A significant subset of conference attendees concluded that there is a realistic...
Article
The Joint Workshop on Induced Special Regions convened scientists and planetary protection experts to assess the potential of inducing special regions through lander or rover activity. An Induced Special Region is defined as a place where the presence of the spacecraft could induce water activity and temperature to be sufficiently high and persist...
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Microbial life permeates Earth's critical zone and has likely inhabited nearly all our planet's surface and near subsurface since before the beginning of the sedimentary rock record. Given the vast time that Earth has been teeming with life, do astrobiologists truly understand what geological features untouched by biological processes would look li...
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The surface of Mars has been well mapped and characterized, yet the subsurface — the most likely place to find signs of extant or extinct life and a repository of useful resources for human exploration — remains unexplored. In the near future this is set to change.
Preprint
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Methane oxidizing microorganisms (methanotrophs) are a major sink for the greenhouse gas methane (CH 4 ), and have been investigated in several environments. Recent studies show that CH 4 consumption in caves is pervasive and is a result of active methanotrophy. However, little is known about what controls the distribution and abundance of methanot...
Conference Paper
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Many meteorites have been identified on the Martian surface by the MER rovers [1-4] and the Mars Science Laboratory (MSL) rover Curiosity [5-7]. These Martian finds are different from the SNC meteorites that are fragments of Martian crust found on Earth, and often referred to as Martian meteorites. The Martian finds can significantly enhance unders...
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The search for life and habitable environments on other Solar System bodies is a major motivator for planetary exploration. Due to the difficulty and significance of detecting extant or extinct extraterrestrial life in situ, several independent measurements from multiple instrument techniques will bolster the community's confidence in making any su...
Chapter
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The Guadalupe Mountains consist of an uplift of Permian carbonate shelf deposits in a semiarid landscape. A variety of speleogenetic processes, mostly hypogene, have made them one of the world’s best-known cave regions. The most notable caves are Carlsbad Cavern, which contains the largest known cave room in the USA, and Lechuguilla Cave, now the w...
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Methane (CH4) is an economic resource and a greenhouse gas, but its migration through rocks is not immediately associated with speleogenesis. Sulfuric acid speleogenesis is a cave forming mechanism that has produced a variety of economically important oil fields and aquifers and is theorized to be related to the oxidation of CH4 and hydrocarbons. D...
Conference Paper
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Microbial mats are a prominent feature in many Hawaiian lava caves, but little research has been done on these communities. Since 2008, we have sampled the microbial communities in16 lava caves on the Big Island ofHawaìi to conduct scanning electron microscopy (SEM) analysis, cultivation, and DNA sequencing. These caves occurred in areas ofHawaìi t...
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Speleothems frequently host “fossil” fluids that were trapped in small inclusions during growth. Such fluids may provide valuable clues to past microbial, geochemical, and climatic processes during their formation. However, one difficulty is to understand which gases represent background atmosphere and fluids within a given cave system at a particu...
Article
Fossil microbes are generally preserved by authigenic minerals, including silica, apatite, iron minerals, clays, and carbonates. An alternative mode of preservation by entombment in calcite, without replacement, has been identified in carbonate cave pool microbialites that were etched and examined in the scanning electron microscope (SEM). Features...
Article
The COSPAR Planetary Protection Policy describes requirements for different planetary protection categories depending on the type of mission, the target body and the type of scientific investigations [1]. Updating the COSPAR Planetary Protection Policy is an iterative process that involves the scientific community. This process is based on new scie...
Conference Paper
Interest in possible caves or karst terrain on other bodies in the Solar System has grown over the past decade or two spurred on by detection of apparent volcanic caves on the Moon, Mars, Io, Venus, and Mercury seemingly produced by processes resembling those on Earth. Additionally, extremely cold icy bodies like Titan, Europa, or Enceladus may exh...
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Previous reports of reticulated filaments, an unknown microbe, document that they are ubiquitous in subsurface environments, including limestone caves, lava tubes, and even granite tunnels. Although initial reports of fossil reticulated filaments described preserved organic matter, additional instances involve replacement by calcite, Mn-oxides, sil...
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We discuss the development of a portable NIR reflectance point spectrometer based on acousto-optic tunable filter (AOTF) technology for future in situ geologic investigations of planetary surfaces. AOTFs are low power devices that operate on the principle of diffraction in a birefringent crystal. We have demonstrated the efficacy of this technique...
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Phytoliths are plant-derived mineral bodies.They have been used in a variety of archaeological, environmental, and climate studies to infer paleoclimate from the vegetation types represented by diagnostic phytolith morphologies.Phytoliths can be recovered from modern plants, soils, sediments, lacustrine deposits, eolian deposits, archaeological sit...
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Mud and soil deposits occur in many caves. Frequently, they are transported into caves by flooding or infilling. However, in several caves around the world, soil-like material has been found that appears to be an autochthonous product of pedogenic or soil-forming processes that take place in these caves. The podegenic alteration of bedrock results...
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A committee of the Mars Exploration Program Analysis Group (MEPAG) has reviewed and updated the description of Special Regions on Mars as places where terrestrial organisms might replicate (per the COSPAR Planetary Protection Policy). This review and update was conducted by an international team (SR-SAG2) drawn from both the biological science and...
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Conspicuous sulfide-rich karst springs flow from Cretaceous carbonates in northern Sierra de Chiapas, Mexico. This is a geologically complex, tropical karst area. The physical, geologic, hydrologic and chemical attributes of these springs were determined and integrated into a conceptual hydrogeologic model. A meteoric source and a recharge elevatio...
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The question of whether there is or was life on Mars has been one of the most pivotal since Schiaparellis' telescopic observations of the red planet. With the advent of the space age, this question can be addressed directly by exploring the surface of Mars and by bringing samples to Earth for analysis. The latter, however, is not free of problems....
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Many copper water lines for municipal drinking water in Santa Fe, New Mexico USA, have developed pinhole leaks. The pitting matches the description of Type I pitting of copper, which has historically been attributed to water chemistry and to contaminants on the copper tubing surface. However, more recent studies attribute copper pitting to microbia...
Conference Paper
We demonstrate the biosignature detection capabilities of several classes of instruments, including a compact laser desorption/ionization time-of-flight mass spectrometer, an acousto-optic tunable filter IR point spectrometer, a laser-induced breakdown spectrometer, and a scanning electron microscope. We collected biotic and abiotic calcite, gypsum...
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Rock varnish is a thin dark coating best known from deserts, and is believed to grow extremely slowly. Varnish samples from near Socorro, New Mexico (United States), contain as much as 3.7% Pb0, derived from nearby smelters operating from A.D. 1870 to 1931. Additional varnish, measuring as much as 4 mu m beyond the Pb-rich layer, indicates continue...
Chapter
Lava caves represent a scientifically untapped habitat in which to study Earth’s microbial life and provide an outstanding environment in which to identify biosignatures for detecting life on other planets. Our studies of microbial mats and mineral deposits in lava caves in the Azores (Portugal), New Mexico, and Hawai‘i (USA) have revealed a wealth...
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First International Planetary Cave Research Workshop: Implications for Astrobiology, Climate, Detection, and Exploration; Carlsbad, New Mexico, 25-28 October 2011 With the advent of high-resolution spatial imaging, the idea of caves on other planets has moved from the pages of science fiction into the realm of hard-core science—complete with hypoth...
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We discuss the development of a miniature near-infrared point spectrometer, operating between 1.7–3.45 μm, based on acousto-optic tunable filter (AOTF) technology. This instrument may be used to screen and corroborate analyses of samples containing organic biomarkers or mineralogical signatures suggestive of extant or extinct organic material colle...
Article
Moving beyond studies of the invertebrate and vertebrate life to the microbial life that inhabits lava caves has allowed us to open up a whole new realm of research into life in Earth’s extreme habitats. Our studies are laying the foundation to allow us to understand the lava cave ecosystem better, and in time, we may be able to shed light on what...
Article
Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contain...
Conference Paper
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We discuss the development of a miniature near-infrared point spectrometer, operating in the 1.7-4 mm region, based on acousto-optic tunable filter (AOTF) technology. This instrument may be used to screen and corroborate analyses of samples containing organic biomarkers or mineralogical signatures suggestive of extant or extinct organic material co...
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Scientists vigorously debate the degree to which rock varnish is formed through the actions of microorganisms. To investigate this enigma, we utilized a three-pronged approach that combined (1) culture-independent molecular methods to characterize bacterial communities associated with varnish that coats the rhyolitic volcanic rocks of Black Canyon,...
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Biologically influenced speleothems (biothems) and microbial breakdown products (speleosols) display a set of important unifying properties with predictive power for the subsurface systems of unknown worlds.
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A macro- to microscopic biosignature suite from Pleistocene cave pool speleothems indicates that long term preservation of actual organic matter is possible in cave speleothems and perhaps in the subsurface of other planets.
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In addition to clearly biological microbial mats, lava tubes contain many non-biological appearing mineral deposits that contain life. The discovery that such deposits contain abundant life can help guide our detection of life on other extrater-restrial bodies.
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Physical and geochemical biosignatures across volcanic environmental gradients on Earth show how such conditions alter the detectable products of microorganisms and provide targets for life detection experiments on future planetary missions.
Chapter
Introduction: Mars missions to date have interrogated the planet at very large scales using orbital platforms or at very small scales intensively studying relatively small patches of terrain. In order to facilitate discovery and eventual utilization of Martian resources for future missions, a strategy that will bridge these scales and allow assessm...