Colin F. Wilson

• DPhil
• Project Scientist at European Space Agency

Plain Language Summary Atmospheric gravity waves (AGW) are wave‐like disturbances that travel through a planet's atmosphere, much like waves moving across water's surface. These waves influence weather patterns and the overall behavior of the atmosphere. Studying them on Mars helps us understand not only the Martian atmosphere but also provides ins...

Plain Language Summary Radio occultation is a measuring technique involving the passage of a signal through an atmosphere, during which we observe how much the signal bends. This bending effect is precisely measured as a frequency shift. Typically, this technique is employed by transmitting a signal from a satellite orbiting a planet to a ground st...

This work reviews possible signatures and potential detectability of present-day volcanically emitted material in the atmosphere of Venus. We first discuss the expected composition of volcanic gases at present time, addressing how this is related to mantle composition and atmospheric pressure. Sulfur dioxide, often used as a marker of volcanic acti...

Launched on 2 June 2003 and arriving at Mars on 25 December 2003 after a 7-month interplanetary cruise, Mars Express was the European Space Agency’s first mission to arrive at another planet. After more than 20 years in orbit, the spacecraft and science payload remain in good health and the mission has become the second oldest operational planetary...

The S1222a marsquake detected by InSight on 4 May 2022 was the largest of the mission, at MwMa ${M}_{w}^{Ma}$ 4.7. Given its resemblance to two other large seismic events (S1000a and S1094b), which were associated with the formation of fresh craters, we undertook a search for a fresh crater associated with S1222a. Such a crater would be expected to...

In this work we discuss various selected mission concepts addressing Venus evolution through time. More specifically, we address investigations and payload instrument concepts supporting scientific goals and open questions presented in the companion articles of this volume. Also included are their related investigations (observations & modeling) an...

Spacecraft-to-spacecraft radio occultations experiments are being conducted at Mars between the Mars Express (MEX) and Trace Gas Orbiter (TGO) spacecraft, the first ever periodic inter-spacecraft occultations at a planet other than Earth. Here we present results from the first 83 such occultations, conducted between 2\textsuperscript{nd} Nov 2020 a...

Despite the growing importance of planetary Space Weather forecasting and radiation protection for science and robotic exploration and the need for accurate Space Weather monitoring and predictions, only a limited number of spacecraft have dedicated instrumentation for this purpose. However, every spacecraft (planetary or astronomical) has hundreds...

Venus today is inhospitable at the surface, its average temperature of 750 K being incompatible to the existence of life as we know it. However, the potential for past surface habitability and upper atmosphere (cloud) habitability at the present day is hotly debated, as the ongoing discussion regarding a possible phosphine signature coming from the...

Venus is the planet in the Solar System most similar to Earth in terms of size and (probably) bulk composition. Until the mid-20th century, scientists thought that Venus was a verdant world—inspiring science-fictional stories of heroes battling megafauna in sprawling jungles. At the start of the Space Age, people learned that Venus actually has a h...

The mid‐infrared channel of the Atmospheric Chemistry Suite (ACS MIR) onboard the ExoMars Trace Gas Orbiter is capable of observing the infrared absorption of ozone (O3) in the atmosphere of Mars. During solar occulations, the 003←000 band (3,000‐3,060 cm⁻¹) is observed with spectral sampling of ∼0.045 cm⁻¹. Around the equinoxes in both hemispheres...

The history of in-situ Venus exploration has been limited to a few opportunities with different probes that were capable to operate, for short periods of time, under the extreme atmospheric conditions of the planet. Among these missions, the VeGa balloons deployed in the Venus atmosphere in the mid-eighties of previous century revealed the advantag...

Mars Express With almost two decades of Mars observation behind it, Mars Express remains a dependable and highly productive mission. Recent science highlights include (1) continued mapping of subsurface reflectors beneath the south polar layered ice deposits, and associated work to explain the cause of these reflections; (2) a global map of mineral...

On June 10, 2021, the European Space Agency (ESA) announced the selection of EnVision as its newest medium-class science mission. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus [1, 2]. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of re...

Context. Reports on the detection of methane in the Martian atmosphere have motivated numerous studies aiming to confirm or explain its presence on a planet where it might imply a biogenic or more likely a geophysical origin. Aims. Our intent is to complement and improve on the previously reported detection attempts by the Atmospheric Chemistry Su...

Context. The detection of sulphur species in the Martian atmosphere would be a strong indicator of volcanic outgassing from the surface of Mars. Aims. We wish to establish the presence of SO2, H2S, or OCS in the Martian atmosphere or determine upper limits on their concentration in the absence of a detection. Methods. We perform a comprehensive a...

Context. The detection of sulphur species in the Martian atmosphere would be a strong indicator of volcanic outgassing from thesurface of Mars.Aims. We wish to establish the presence of SO2, H2S, or OCS in the Martian atmosphere or determine upper limits on their concen-tration in the absence of a detection. Methods. We perform a comprehensive anal...

Isotopic ratios in atmospheric CO2 are shaped by various processes throughout Mars' history, and can help understand what the atmosphere of early Mars was like to sustain liquid water on its surface. In this study, we monitor the O and C isotopic composition of CO2 between 70 and 130 km for more than half a Martian year using solar occultation obse...

The detection of sulphur species in the Martian atmosphere would be a strong indicator of volcanic outgassing from the surface of Mars. We wish to establish the presence of SO2, H2S, or OCS in the Martian atmosphere or determine upper limits on their concentration in the absence of a detection. We perform a comprehensive analysis of solar occultati...

The current Martian atmosphere is about five times more enriched in deuterium than Earth’s, providing direct testimony that Mars hosted vastly more water in its early youth than nowadays. Estimates of the total amount of water lost to space from the current mean D/H value depend on a rigorous appraisal of the relative escape between deuterated and...

NASA’s Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonfly's science themes include investigation of Titan’s prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based “life as we know it” (as might occur in the interior mantle ocean, potential cryovolcanic flows, an...

The detection of phosphine (PH₃) in the atmosphere of Venus has been recently reported on the basis of millimetre-wave radio observations and their reanalyses. In this Matters Arising we perform an independent reanalysis, identifying several issues in the interpretation of the spectroscopic data. As a result, we determine sensitive upper limits for...

In this paper, originally submitted in answer to ESA’s “Voyage 2050” call to shape the agency’s space science missions in the 2035–2050 timeframe, we emphasize the importance of a Venus exploration programme for the wider goal of understanding the diversity and evolution of habitable planets. Comparing the interior, surface, and atmosphere evolutio...

A lightweight, low-power instrument package to measure, in situ, both (1) the local gaseous environment and (2) the composition and microphysical properties of attendant venusian aerosols is presented. This Aerosol-Sampling Instrument Package (ASIP) would be used to explore cloud chemical and possibly biotic processes on future aerial missions such...

Venus Corona and Tessera Explorer (VeCaTEx) would use an aerobot to descend repeatedly beneath the dense clouds for imaging targeted area of the surface in the near infrared to address six of the prime investigations prioritized by VEXAG. The technologies needed could be matured during the next decade.

Understanding Venus will benefit from a dedicated effort through an international program of missions that are coordinated and offering opportunities for coooperation. The recent discovery of phosphene in the Venus clouds and possibility of life will increase the exploration missions and cooperation and coordination will be very benefical.

Ultraviolet spectral imaging has been a powerful tool to investigate the cloud top of Venus, allowing for measurement of several minor gases (especially SO2, SO, O3), of cloud top aerosol’s microphysical properties and of atmospheric dynamics through tracking of the unevenly distributed UV absorber. After a brief review of recent UV instruments tha...

Hydrogen chloride was discovered in the atmosphere of Mars for the first time during the global dust storm in Mars year (MY) 34 (July 2018) using the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) on the ExoMars Trace Gas Orbiter. The simultaneity of variations in dust and HCl, and a correlation between water vapour and HCl, led to the...

Carbon monoxide (CO) is the main product of CO2 photolysis in the Martian atmosphere. Production of CO is balanced by its loss reaction with OH, which recycles CO into CO2. CO is therefore a sensitive tracer of the OH-catalysed chemistry that contributes to the stability of CO2 in the atmosphere of Mars. To date, CO has been measured only in terms...

This paper traces the history of the Oxford Magnetic Suspension and Balance System, from its initial development in the 1960s through to current times. Developed in conjunction with the Oxford Low Density Tunnel, the balance has been a key instrument throughout its history for investigating aerodynamic forces at high Mach numbers, low density flows...

More than 85% of the 23 investigations developed by VEXAG are largely accomplished via a NF mission centered on a variable-altitude balloon (aerobot) supported by a science/comm orbiter. Circling Venus >15 times over ~90 days, the aerobot repeatedly visits 52–62 km alts as it semi-continuously samples a host of environmental & surface parameters.

The Thalassa mission concept was developed in response to the 2019 NASA Planetary Mission Concept Studies call. Using a multi-platform mission architecture, Thalassa seeks to address a single science goal: to determine the extent to which water has played a role in the geological evolution of Venus.

The current Martian atmosphere is about five times more enriched in deuterium than Earth's, providing a direct testimony that Mars hosted several times more water in its early youth than nowadays. Estimates of the total amount of water lost to space from the current mean D/H value depend on a rigorous appraisal of the relative escape between deuter...

The detection of phosphine (PH3) has been recently reported in the atmosphere of Venus employing mm-wave radio observations (Greaves et at. 2020). We here demonstrate that the observed PH3 feature with JCMT can be fully explained employing plausible mesospheric SO2 abundances (~100 ppbv as per the SO2 profile given in their figure 9), while the ide...

The detection of phosphine (PH₃) has been recently reported in the atmosphere of Venus employing mm-wave radio observations (Greaves et at. 2020). We here demonstrate that the observed PH₃ feature with JCMT can be fully explained employing plausible mesospheric SO₂ abundances (~100 ppbv as per the SO₂ profile given in their figure 9), while the ide...

In this presentation we will describe recent work to model upward and downward fluxes of solar and thermal radiation in the atmosphere of Venus using the NEMESIS radiative transfer and retrieval tool (Irwin et al., JQSRT, 109, 1136, 2008). Using a plane-parallel matrix operator multiple-scattering model we simulate the internal 3D radiation field w...

The Atmospheric Chemistry Suite (ACS) [1], one of the four science experiments on board ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission has started science operations in March 2018. ACS consists of 3 infrared spectrometers targeting the unambiguous detection of trace gases of potential geophysical or biological interest. The dataset repo...

An exciting and novel science mission concept called Seismic and Atmospheric Exploration of Venus (SAEVe) has been developed which uses high-temperature electronics to enable a three-order magnitude increase in expected surface life (120 Earth days) over what has been achieved to date. This enables study of long-term, variable phenomena such as the...

Water reaches Mars' upper atmosphere Mars once hosted abundant water on its surface but subsequently lost most of it to space. Small amounts of water vapor are still present in the atmosphere, which can escape if they reach sufficiently high altitudes. Fedorova et al. used data from the ExoMars Trace Gas Orbiter spacecraft to determine the distribu...

The VenSpec-H instrument is part of the EnVision M5 mission payload which has been selected by ESA to enter Phase A in January 2019 for a potential mission selection in 2021. EnVision is a medium class mission to determine the nature and current state of geological activity on Venus, and its relationship with the atmosphere, to understand how Venus...

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the A...

ACS (the Atmospheric Chemistry Suite) [1] instrument onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO) is dedicated to measurements of the Martian atmosphere, in particular implementing the solar occultation technique for sensitive measurement of trace atmospheric gases TGO has started science observations from April 2018 (Ls=162°; MY34), a...

As we become aware of Earth's changing climate, and as we discover terrestrial planets in other solar systems, we gain ever more reasons to study the Earth's nearest neighbour and closest sibling, the only Earth-sized planet besides our own that can be reached by our spacecraft. For the scientific and programmatic reasons outlined in this document,...

The surname of author Cathy Quantin-Nataf was misspelled ‘Quantin-Nata’ , authors Ehouarn Millour and Roland Young were missing from the ACS Science Team list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

The surname of author Cathy Quantin-Nataf was misspelled ‘Quantin-Nata’, authors Ehouarn Millour and Roland Young were missing from the ACS and NOMAD Science Teams list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere³, primarily owing to solar heating of the dust³. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications...

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today¹. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations2–5. These measurements, however, are di...

One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenic species in Venus’ atmosphere, one of the most prominent being sulphur dioxide (SO2). Monitoring SO2 below the clouds can be performed on the night-side near 2.4μm, and is one science objective of the VenSpec-H channel (P.I.: A. C. Vandaele, BIRA...

EnVision [1,2] is a Venus orbiter mission that will determine the nature and current state of geological activity on Venus, and its relationship with the atmosphere, to understand how and why Venus and Earth evolved so differently. Envision is a finalist in ESA’s M5 Space Science mission selection process, and is being developed in collaboration wi...

More than three decades have passed since the publication of the last review of the Venus clouds and hazes. The paper published in 1983 in the Venus book summarized the discoveries and findings of the US Pioneer Venus and a series of Soviet Venera spacecraft (Esposito et al. in Venus, p. 484, 1983). Due to the emphasis on in-situ investigations fro...

The first of the two missions foreseen in the ExoMars program was successfully launched on 14th March 2016. It included the Trace Gas Orbiter and the Schiaparelli Entry descent and landing Demonstrator Module. Schiaparelli hosted the DREAMS instrument suite that was the only scientific payload designed to operate after the touchdown. DREAMS is a me...

Despite the tremendous progress that has been made since the publication of the Venus II book in 1997, many fundamental questions remain concerning Venus’ history, evolution and current geologic and atmospheric processes. The international science community has taken several approaches to prioritizing these questions, either through formal processe...

The DREAMS (Dust characterization, Risk assessment and Environment Analyser on the Martian Surface) instrument on Schiaparelli lander of ExoMars 2016 mission was an autonomous meteorological station designed to completely characterize the Martian atmosphere on surface, acquiring data not only on temperature, pressure, humidity, wind speed and its d...

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric de...

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to...

Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is...

The vertical distribution of sulfur species in the Venus atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets – SPICAV/UV nadir observatio...

The Venus International Reference Atmosphere (VIRA) model contains tabulated values of temperature and number densities obtained by the experiments on the Venera entry probes, Pioneer Venus Orbiter and multi-probe missions in the 1980s. The instruments on the recent Venus Express orbiter mission generated a significant amount of new observational d...

Why are the terrestrial planets so different? Venus should be the most Earth-like of all our planetary neighbours. Its size, bulk composition and distance from the Sun are very similar to those of the Earth. Its original atmosphere was probably similar to that of early Earth, with large atmospheric abundances of carbon dioxide and water - possibly...

This document is the EnVision Venus orbiter proposal, submitted in October 2016 in response to ESA's M5 call for Medium-size missions for its Science Programme, for launch in 2029. Why are the terrestrial planets so different? Venus should be the most Earth-like of all our planetary neighbours: its size, bulk composition and distance from the Sun a...

DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface) is a payload accommodated on the Schiaparelli Entry and Descent Module (EDM) of ExoMars 2016, the ESA and Roscosmos mission to Mars (Esposito (2015), Bettanini et al. (2014)). It is a meteorological station with the additional capability to perform meas...