Related papers: A nitrogen-rich atmosphere on ancient Mars consist…
The origin of life on Earth seems to demand a highly reduced early atmosphere, rich in CH4, H2, and NH3, but geological evidence suggests that Earth's mantle has always been relatively oxidized and its emissions dominated by CO2 H2O, and…
It is currently uncertain as to whether methane exists on Mars. Data from the Curiosity Rover suggests a background methane concentration of a few tenths parts per billion whereas data from the Trace Gas Orbiter suggest an upper limit of…
The composition the atmosphere of Venus results from the integration of many processes entering into play over the entire geological history of the planet. Determining the elemental abundances and isotopic ratios of noble gases (He, Ne, Ar,…
Mars is the Solar System's canonical small, rocky planet that transitioned from early geologic activity and surface liquid water to a cold and arid planet with a thin, cold, CO$_2$-dominated atmosphere. The evolution of Mars, in the context…
Mars provides a critical analog to once habitable exoplanets that have since lost their surface liquid water. The current atmospheric state of Mars retains the chemical fingerprints of that transition, including isotopic signatures of…
We apply a 1D upper atmosphere model to study thermal escape of nitrogen over Titan's history. Significant thermal escape should have occurred very early for solar EUV fluxes 100 to 400 times higher than today with escape rates as high as…
Magma ocean crystallisation sets up the early structure and long-term evolution of terrestrial planets. Recent seismic evidence signals the presence of a silicate layer at the base of Mars' mantle. Magma-ocean crystallisation and subsequent…
The earliest atmospheres of rocky planets originate from extensive volatile release during magma ocean epochs that occur during assembly of the planet. These establish the initial distribution of the major volatile elements between…
The adaptability of extremophiles on Earth raises the question of what strategies putative life might have used to adapt to the present conditions on Mars. Here, we hypothesize that organisms might utilize a water-hydrogen peroxide…
Characterizing the Martian atmosphere is an essential objective to understand its meteorology and its climate. The lower atmosphere (< 40 km) and middle atmosphere (40-80 km) of Mars appear dynamically coupled at much higher levels than in…
N2 is abundant in Pluto's atmosphere and on its surface, but the supply is depleted by prodigious atmospheric escape. We demonstrate that cometary impacts could not have delivered enough N mass to resupply Pluto's N2 atmospheric escape over…
Escape of an early atmosphere from Titan, during which time NH3 could be converted by photolysis into the present N2 dominated atmosphere, is an important problem in planetary science. Recently Gilliam and Lerman (2014) estimated escape…
Carbon dioxide (CO$_2$) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions.…
We consider super-Earth sized planets which have a water mass fraction that is large enough to form an external mantle composed of high pressure water ice polymorphs and that lack a substantial H/He atmosphere. We consider such planets in…
Uranus provides a unique laboratory to test our understanding of planetary atmospheres under extreme conditions. Multi-spectral observations from Voyager, ground-based observatories, and space telescopes have revealed a delicately banded…
Active dark flows known as recurring slope lineae have been observed on the warmest slopes of equatorial Mars. The morphology, composition and seasonality of the lineae suggest a role of liquid water in their formation. However, internal…
The discovery of thousands of highly irradiated, low-mass, exoplanets has led to the idea that atmospheric escape is an important process that can drive their evolution. Of particular interest is the inference from recent exoplanet…
We used chemical equilibrium and chemical kinetic calculations to model chemistry of the volatiles released by heating different types of carbonaceous, ordinary and enstatite chondritic material as a function of temperature and pressure.…
Volatile molecules containing hydrogen, carbon, and nitrogen are key components of planetary atmospheres. In the pebble accretion model for rocky planet formation, these volatile species are accreted during the main planetary formation…
The case for a much warmer climate on the early Earth than now is presented. The oxygen isotope record in sedimentary chert and the compelling case for a near constant isotopic oxygen composition of seawater over geologic time support…