from New Scientist Space
Hints of huge water reservoirs on Mars – space
Mars is losing little water to space, according to new research, so much of its ancient abundance may still be hidden beneath the surface.
Dried up riverbeds and other evidence imply that Mars once had enough water to fill a global ocean more than 600 metres deep, together with a thick atmosphere of carbon dioxide that kept the planet warm enough for the water to be liquid. But the planet is now very dry and has a thin atmosphere.
Some scientists have proposed that the Red Planet lost its water and CO2 to space as the solar wind stripped molecules from the top of the planet’s atmosphere. Measurements by Russia’s Phobos-2 probe to Mars in 1989 hinted that the loss was quite rapid.
Now the European Space Agency’s Mars Express spacecraft has revealed that the rate of loss is much lower. Stas Barabash of the Swedish Institute of Space Physics in Kiruna led a team that used data from Mars Express’s ASPERA-3 instrument (Analyzer of Space Plasmas and Energetic Atoms).
Its measurements suggest the whole planet loses only about 20 grams per second of oxygen and CO2 to space, only about 1% of the rate inferred from Phobos-2 data.
If this rate has held steady over Mars’s history, it would have removed just a few centimetres of water, and a thousandth of the original CO2.
Either some other process removed the water and CO2 or they are still present and hidden somewhere on Mars, probably underground, Barabash says. “We are talking about huge amounts of water,” he told New Scientist. “To store it somewhere requires a really big, huge reservoir.”
Barabash is not sure what form this reservoir or reservoirs would take, but he points to findings from NASA’s now lost Mars Global Surveyor (MGS). This data provided evidence that water had gushed down slopes on Mars in recent years, possibly originating from beneath the surface (see Water flows on Mars before our very eyes). “So there might be some possibilities for water existing in liquid form even now,” he says.
“If water is there, I think it will put all ideas about human missions to Mars on a completely different level,” he says. “It’s not only water to support [astronauts], but also a potential fuel.” Hydrogen and oxygen for rocket fuel can be produced from water.
However, the researchers point out that other mechanisms might have removed water and CO2 from Mars, such as asteroid and comet impacts. Or the solar wind might have sheared off of whole chunks of atmosphere rather than individual molecules.
Another possibility is suggested by Mars atmosphere expert David Brain at the University of California in Berkeley, US. He points out that magnetic storms might boost the rate at which the solar wind strips molecules from the atmosphere.
“We believe that solar storms were frequent and more intense early on in the solar system’s history,” he told New Scientist. Even so, Brain thinks that some of Mars’s ancient water and CO2 is still stored in hidden reservoirs.