Mars is known for its thin atmosphere, where CO2dominates and provides most of the atmospheric mass and pressure.
But what about water?
Water on Marsis currently found on the surfaceas a layer of ice several kilometers thick at the north pole.
Nevertheless, the Martian atmosphere is extremely dry compared to Earths, with about 100 times less water.
New datanow provides a better understanding of why there is (almost) no water left on Mars.
There is plenty of evidence of water on Marss surface in the distant past about four billion years ago.
It is indeed thisloss of gas to spacethat helps explain the current tenuousness of Mars atmosphere.
Martian water has a very specific chemical composition.
This is interpreted as the result of the loss of hydrogen, gradually leaving behind the heavier isotopes.
In particular, it tells us more about the intermediate processes by which hydrogen and deuterium enter the exosphere.
Whatour recent studyreveals is that condensation plays a minor role in the deuterium content of the exosphere.
Only the Trace Gas Orbiter satellite can reveal the joint concentrations of H20 and HDO.
Butthe NASA satellite MAVENis able to observe and characterize hydrogen and deuterium populations in the exosphere.
The concomitance of these two missions is bringing to life a new line of research.
