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The absence of global magnetic fields is often cited to explain why Mars lacks a dense atmosphere. This line of thought is based on a prevailing theory that magnetic fields can shield the atmosphere from solar wind erosion. However, we…
Early Mars may have had a warmer and denser atmosphere allowing for the presence of liquid water on the surface. However, climate model studies have not been able to reproduce these conditions even with a CO2 atmosphere of several bars.…
Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study…
The lunar history of water deposition, loss, and transport post-accretion has become an important consideration in relation to the possibility of a human outpost on the Moon. Very recent work has shown that a secondary primordial atmosphere…
The detection of biologically important, organic molecules on Mars is an important goal that may soon be reached. However, the current small number of organic detections at the Martian surface may be due to the harsh UV and radiation…
Observations show that the lower thermosphere of Mars ($\sim$100--140 km) is up to 40 K colder than the current general circulation models (GCMs) can reproduce. Possible candidates for physical processes missing in the models are larger…
Mars' sedimentary rocks record Gyrs of environmental change. New data enable the first global analysis of paleo-environment relevant physical properties of these rocks, including layer thickness and accumulation rate. We find that layer…
Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluvio-lacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand…
We discuss 3D global simulations of the early Martian climate that we have performed assuming a faint young Sun and denser CO2 atmosphere. We include a self-consistent representation of the water cycle, with atmosphere-surface interactions,…
Despite decades of scientific research on the subject, the climate of the first 1.5 Gyr of Mars history has not been fully understood yet. Especially challenging is the need to reconcile the presence of liquid water for extended periods of…
Ancient hydrology is recorded by sedimentary rocks on Mars. The most voluminous sedimentary rocks that formed during Mars' Hesperian period are sulfate-rich rocks, explored by the $Opportunity$ rover from 2004-2012 and soon to be…
We compare estimates of atmospheric precipitation during the Martian Noachian-Hesperian boundary 3.8 Gyr ago as calculated in a radiative-convective column model of the atmosphere with runoff values estimated from a geomorphological…
The formation of gullies on Mars has often been attributed to the melting of (sub)surface water ice. However, melting-based hypotheses generally overlook key processes: (1) sublimation cooling by latent heat absorption, (2) the…
Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface. While the high D/H ratios (~6 times the Earth's ocean water) of the current martian atmosphere suggest that significant…
Mars is believed to have had a substantial atmosphere in the past. Atmospheric loss led to depressurization and cooling, and is thought to be the primary driving force responsible for the loss of liquid water from its surface. Recently,…
The presence of the ancient valley networks on Mars indicates that the climate at 3.8 Ga was warm enough to allow substantial liquid water to flow on the martian surface for extended periods of time. However, the mechanism for producing…
Remote sensing data from orbiter missions have proposed that ground ice may currently exist on Mars, although the volume is still uncertain. Recent analyses of Martian meteorites have suggested that the water reservoirs have at least three…
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…
River deposits are one of the main lines of evidence that tell us that Mars once had a climate different from today, and so changes in river deposits with time tell us something about how Mars climate changed with time. In this study, we…
Whether extant life exists in the martian subsurface is an open question. High concentrations of photochemically produced CO and H2 in the otherwise oxidizing martian atmosphere represent untapped sources of biologically useful free energy.…