Liquid water is currently unstable on the surface of Mars because the planet's atmosphere is too thin and temperatures are too cold. But once on the Red Planet, there were warm and humid conditions in which life could develop. An important challenge facing planetary science is the dating of the period when radical changes in climatic conditions occurred on Mars, which made the planet as dry and lifeless as it is today.
In a new study, cosmochemist Bill Cassata of Livermore National Laboratory. E. Lawrence, USA, shows that it is possible to impose a limitation on the duration of the "water period" of the history of Mars by examining the gases contained in Martian meteorites.
Cassata analyzed the content of one of the gases in the Martian atmosphere, xenon (Xe), in two Martian meteorites, ALH 84001 and NWA 7034. The results of the analysis indicate that in the early Martian history there was enough hydrogen in the planet's atmosphere to make it possible to separate xenon isotopes by mass (lighter isotopes are removed into space) through a process known as the hydrodynamic mechanism of atmospheric loss. However, Cassata's measurements show that this process culminated in the first few hundred million years after the planet's formation (more than 4 billion years ago), and since then the xenon isotopic composition of the Martian atmosphere has remained almost unchanged.
On Earth, the separation of xenon isotopes by mass is a gradual process that continues to slowly continue to this day. The fact that the loss of the atmosphere by the hydrodynamic mechanism stopped on Mars many years ago indicates a reduction in the flow of hydrogen into space, and this, in turn, indicates that there was almost no water on the surface of the Red Planet during this period, photodissociation which is an important source of atmospheric hydrogen. Consequently, the "wet" period in the history of Mars did not last as long as some modern scientists believe, and ended within a few hundred million years after the formation of the planet, Cassata said.
The study was published in the journal Earth and Planetary Science Letters.