杏吧原创

WHAT if Mars hasn鈥檛 lost its water and atmosphere, but is just hiding them beneath the surface?

Dried-up riverbeds and sedimentary rocks suggest that the planet once had enough liquid water to fill a global ocean more than 600 metres deep. It would also have had an atmosphere rich in CO₂ to keep the planet warm and the water liquid. Mars is thought to have lost much of its atmosphere, and consequently its water, to space due to solar wind skimming off molecules.

In 1989, data from the Russian probe Phobos 2 hinted that this loss was quite rapid. Yet Stanislav Barabash of the Swedish Institute of Space Physics in Kiruna and his team analysed data from the Mars Express probe and found that the planet is losing oxygen and CO₂ at the rate of only about 20 grams per second 鈥� just 1 per cent of the rate inferred by Phobos 2. If this rate has held steady over Mars鈥檚 history, just a few centimetres of water and one-thousandth of the original CO₂ would have been lost.

Some other process 鈥� such as asteroid or comet impacts, or intense solar winds boosted by magnetic storms on the sun -could have removed the water and CO₂. Or they could still be on Mars, probably underground. 鈥淲e are talking about huge amounts of water,鈥� says Barabash.