Scientists find new reserves of water on Mars
The Moon is not the only body in the solar system that is wetter than we thought: scientists have also discovered this week that Mars has much more water beneath its surface than was previously known.
Observations of five new Martian craters carved by meteorites have revealed large quantities of water ice, exposed when soil and rock were blown away by the impacts.
While underground Martian ice has been detected before, the new craters where the latest deposits have been found lie roughly midway between the planet’s north pole and its equator, at easily the lowest latitude where it has so far been discovered.
This suggests that the ice sheet beneath the Martian surface may be much more extensive than had been suspected. The ice in the craters also appears to be very pure, containing 99 per cent water.
The discoveries, published in the journal Science, come from an instrument called the the High Resolution Imaging Science Experiment (HiRISE), which is fitted to Nasa’s Mars Reconnaissance Orbiter (MRO). Research showing that the Moon holds small amounts of water at the surface was also published this week by the same journal.
Shane Byrne, of the University of Arizona, a member of the HiRISE team, said of the Mars findings: “This ice is a relic of a more humid climate from perhaps just several thousand years ago. We knew there was ice below the surface at high latitudes of Mars, but we find that it extends far closer to the equator than you would think, based on Mars’s climate today.
“The other surprising discovery is that ice exposed at the bottom of these meteorite impact craters is so pure. The thinking before was that ice accumulates below the surface between soil grains, so there would be a 50-50 mix of dirt and ice. We were able to figure out, given how long it took that ice to fade from view, that the mixture is 1 per cent dirt and 99 per cent ice.” The new craters were detected on August 10 last year, and studied in detail with the HiRISE instrument a month later. “We saw something very unusual ... this bright blue material poking up from the bottom of the crater,” Dr Byrne said. “It looked a lot like water ice. It faded away like you’d expect water ice to fade, because water ice is unstable on Mars’s surface and turns into water vapour in the atmosphere.”
A few days later the Compact Reconnaissance Imaging Spectrometer for Mars picked up the chemical signature of water ice. “All of this had to happen very quickly because 200 days after we first saw the ice, it was gone — it was the colour of dirt,” Dr Byrne said. “If we had taken HiRISE images just a few months later, we wouldn’t have noticed anything unusual. This discovery would have passed us by.”
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