How obliquity has differently shaped Pluto's and Triton's landscapes and climates.

Triton and Pluto are believed to share a common origin, both forming initially in the Kuiper Belt but Triton being later captured by Neptune. Both objects display similar sizes, densities, and atmospheric and surface ice composition, with the presence of volatile ices N, CH, and CO. Yet their appearance, including their surface albedo and ice distribution strongly differ.

Soil Thermophysical Properties Near the InSight Lander Derived From 50 Sols of Radiometer Measurements.

Measurements from the InSight lander radiometer acquired after landing are used to characterize the thermophysical properties of the Martian soil in Homestead hollow. This data set is unique as it stems from a high measurement cadence fixed platform studying a simple well-characterized surface, and it benefits from the environmental characterization provided by other instruments. We focus on observations acquired before the arrival of a regional dust storm (near Sol 50), on the furthest observed patch of soil (i.

Equatorial mountains on Pluto are covered by methane frosts resulting from a unique atmospheric process.

Pluto is covered by numerous deposits of methane, either diluted in nitrogen or as methane-rich ice. Within the dark equatorial region of Cthulhu, bright frost containing methane is observed coating crater rims and walls as well as mountain tops, providing spectacular resemblance to terrestrial snow-capped mountain chains. However, the origin of these deposits remained enigmatic.

Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season.

The loss of water from Mars to space is thought to result from the transport of water to the upper atmosphere, where it is dissociated to hydrogen and escapes the planet. Recent observations have suggested large, rapid seasonal intrusions of water into the upper atmosphere, boosting the hydrogen abundance. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution by altitude.

Publisher Correction: No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations.

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.

Publisher Correction: Martian dust storm impact on atmospheric HO and D/H observed by ExoMars Trace Gas Orbiter.

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.

Martian dust storm impact on atmospheric HO and D/H observed by ExoMars Trace Gas Orbiter.

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

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations.

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane.

Methane on Mars and Habitability: Challenges and Responses.

Recent measurements of methane (CH) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH with peak abundances of ∼7 ppbv.

Dunes on Pluto.

The surface of Pluto is more geologically diverse and dynamic than had been expected, but the role of its tenuous atmosphere in shaping the landscape remains unclear. We describe observations from the New Horizons spacecraft of regularly spaced, linear ridges whose morphology, distribution, and orientation are consistent with being transverse dunes. These are located close to mountainous regions and are orthogonal to nearby wind streaks.

Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover.

The second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth down to 2 m.

Late Tharsis formation and implications for early Mars.

The Tharsis region is the largest volcanic complex on Mars and in the Solar System. Young lava flows cover its surface (from the Amazonian period, less than 3 billion years ago) but its growth started during the Noachian era (more than 3.7 billion years ago).

Increased insolation threshold for runaway greenhouse processes on Earth-like planets.

The increase in solar luminosity over geological timescales should warm the Earth's climate, increasing water evaporation, which will in turn enhance the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can 'run away' until the oceans have completely evaporated. Through increases in stratospheric humidity, warming may also cause evaporative loss of the oceans to space before the runaway greenhouse state occurs.

Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics.

The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, methane has a photochemical lifetime of several centuries, and is therefore expected to have a spatially uniform distribution on the planet.

Heterogeneous chemistry in the atmosphere of Mars.

Hydrogen radicals are produced in the martian atmosphere by the photolysis of water vapour and subsequently initiate catalytic cycles that recycle carbon dioxide from its photolysis product carbon monoxide. These processes provide a qualitative explanation for the stability of the atmosphere of Mars, which contains 95 per cent carbon dioxide. Balancing carbon dioxide production and loss based on our current understanding of the gas-phase chemistry in the martian atmosphere has, however, proven to be difficult.

Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data.

Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.

Retrieval of vertical constituents and temperature profiles from passive submillimeter wave limb observations of the Martian atmosphere: a feasibility study.

The investigation of the Martian atmosphere is of key importance for an understanding of the planets present and past. Passive limb observations of thermal radiation at submillimeter wavelengths in the 320-350-GHz range by use of a state-of-the-art satellite receiver on a low Mars orbit allow important parameters such as the mixing ratios of H2O, HDO, 12CO, 13CO, O3, and H2O2 as well as the thermal profile to be retrieved with high precision and unprecedented vertical range and resolution, providing valuable information for better understanding of the planet's water cycle, atmospheric dynamics, and photochemistry. The feasibility of these kinds of measurement is demonstrated by means of model simulations based on realistic atmospheric, spectroscopic, and instrumental parameters.

Recent ice-rich deposits formed at high latitudes on Mars by sublimation of unstable equatorial ice during low obliquity.

Observations from the gamma-ray spectrometer instrument suite on the Mars Odyssey spacecraft have been interpreted as indicating the presence of vast reservoirs of near-surface ice in high latitudes of both martian hemispheres. Ice concentrations are estimated to range from 70 per cent at 60 degrees latitude to 100 per cent near the poles, possibly overlain by a few centimetres of ice-free material in most places. This result is supported by morphological evidence of metres-thick layered deposits that are rich in water-ice and periglacial-like features found only at high latitudes.