The Planetary Society published an amazing animation showing the ancient Mars – how the red planet looked like when there was liquid water on its surface.

Ancient Mars

Ancient Mars: Today, Mars is a cold, extremely arid desert. It also has a very thin atmosphere. But, more than 3 billion years ago, it was warm, wet, and had an atmosphere that could have supported life. This artist’s model shows what the planet may have looked like with global oceans based on today’s topography. Credit: NASA/MAVEN/Lunar and Planetary Institute.

The ancient Mars may have been more hospitable to life than it is now. Scientists think the magnetosphere of Mars collapsed around 3.7 billion years ago, possibly because of numerous asteroid strikes, and it eventually lost its atmosphere due to solar winds. Now, Mars has a very thin atmosphere: the atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi; 6.0 mbar), about only 0.6% of Earth’s mean sea level pressure of 101.3 kilopascals (14.69 psi; 1.013 bar).

But, plenty of evidence suggests that Mars once had liquid water, a key ingredient for life. Rivers, lakes, and seas once covered Mars billions of years ago.

  • In 2015, maps of water in the martian atmosphere suggested that Mars might once have had enough water to cover up to a fifth of the planet (study: Mars’ water vapor mapping by the SPICAM IR spectrometer: Five martian years of observations).
  • In a different 2015 study published on Nature, researchers noted that the shape of some martian pebbles suggests they once rolled dozens of miles down a river, hinting that ancient martian waterways were stable and not merely fleeting streams.
  • Analysis of layers of martian rock suggest that earlier, deeper layers were likely created when Mars had abundant, fresher water.

NASA scientists have determined that a primitive ocean on Mars held more water than Earth’s Arctic Ocean. But, after the collapse of its magnetosphere, the red planet has lost 87 percent of that water to space, like it lost its atmosphere.

Water on Mars today

The poles of Mars
Today Mars has two permanent polar ice caps. During a pole’s winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25-30% of the atmosphere into slabs of CO2 ice (dry ice). When the poles are again exposed to sunlight, the frozen CO2 sublimes, creating enormous winds that sweep off the poles as fast as 400 km/h. These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds. Clouds of water-ice were photographed by the Opportunity rover in 2004. The caps at both poles consist primarily of water ice. Frozen carbon dioxide accumulates as a comparatively thin layer about one meter thick on the north cap in the northern winter only, while the south cap has a permanent dry ice cover about 8 m thick. Photo:

Today, most of the water on Mars is likely frozen away in its polar caps. If all this water ice were to melt, estimates suggest that a sphere the size of the red planet might be covered in about 100 feet (30 meters) of water.

Frozen water can be found also at the mid-latitudes. In 2015, scientists discovered that a giant slab of ice as big as California and Texas combined is buried just beneath the surface of Mars between its equator and north pole. This water didn’t vaporize and lost to space because it is covered in protective layers of dust.

Mars also has water in the form of hydrated minerals (minerals that have water chemically bound to them). Future crewed missions to Mars could extract this water by heating the hydrated minerals.

The Planetary Society

Founded in 1980 by the American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator Carl Sagan (November 9, 1934 – December 20, 1996), the American planetary scientist Bruce C. Murray (November 30, 1931 – August 29, 2013), and the American astronautics engineer and space spokesperson Louis Friedman (born July 7, 1941), The Planetary Society is an American internationally active, non-governmental, nonprofit foundation. It is involved in research, public outreach, and political advocacy for engineering projects related to astronomy, planetary science, and space exploration.


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