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Mars

Is There Water on Mars? (theconversation.com) 21

Evidence is mounting for "a vast reservoir of liquid water" on Mars, according to a new article by Australian National University professor Hrvoje TkalÄiÄ and geophysics associate professor Weijia Sun from the Chinese Academy of Geological Sciences, announcing their recently published paper.

"Using seismic data from NASA's InSight mission, we uncovered evidence that the seismic waves slow down in a layer between 5.4 and 8 kilometres below the surface, which could be because of the presence of liquid water at these depths." Mars is covered in traces of ancient bodies of water. But the puzzle of exactly where it all went when the planet turned cold and dry has long intrigued scientists... Billions of years ago, during the Noachian and Hesperian periods (4.1 billion to 3 billion years ago), rivers carved valleys and lakes shimmered. As Mars' magnetic field faded and its atmosphere thinned, most surface water vanished. Some escaped to space, some froze in polar caps, and some was trapped in minerals, where it remains today. But evaporation, freezing and rocks can't quite account for all the water that must have covered Mars in the distant past.

Calculations suggest the "missing" water is enough to cover the planet in an ocean at least 700 metres deep, and perhaps up to 900 metres deep. One hypothesis has been that the missing water seeped into the crust. Mars was heavily bombarded by meteorites during the Noachian period, which may have formed fractures that channelled water underground. Deep beneath the surface, warmer temperatures would keep the water in a liquid state — unlike the frozen layers nearer the surface.

In 2018, NASA's InSight lander touched down on Mars to listen to the planet's interior with a super-sensitive seismometer. By studying a particular kind of vibration called "shear waves", we found a significant underground anomaly: a layer between 5.4 and 8 kilometres down where these vibrations move more slowly. This "low-velocity layer" is most likely highly porous rock filled with liquid water, like a saturated sponge. Something like Earth's aquifers, where groundwater seeps into rock pores. We calculated the "aquifer layer" on Mars could hold enough water to cover the planet in a global ocean 520-780m deep.

InSight's seismometer captured vibrations between the crust of Mars and its lower layers from two meteorite impacts in 2021 and a Marsquake in 2022. "These signatures let us pinpoint boundaries where rock changes, revealing the water-soaked layer 5.4 to 8 kilometres deep."

It's an exciting possibility. "Purified, it could provide drinking water, oxygen, or fuel for rockets." And since microbes thrives on earth in deep rocks filled with water, "Could similar life, perhaps relics of ancient Martian ecosystems, persist in these reservoirs?"

Is There Water on Mars?

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