Vast deposits of what appear to be finely layered stacks of water ice and dust extend from the poles to latitudes of about 80 degrees in both Martian hemispheres. Late in the year, Mars Express also spied a huge, icy zone in the Red Planet's Korolev Crater. Its underground location is reminiscent of similar underground lakes in Antarctica, which have been found to host microbes. (Some reports describe it as a "lake," but it's unclear how much regolith is inside the water.) This body of water is said to be about 12.4 miles (20 km) across. In 2018, the European Space Agency's Mars Express spacecraft detected what could be a slurry of water and grains underneath icy Planum Australe. Some craters have unusual-looking deposits of debris around them resembling solidified mudflows, potentially indicating that the impactor hit underground water or ice. Some volcanoes also have just a few craters, which suggests they erupted recently, with the resulting lava covering up any old craters. Much of the surface of the southern hemisphere is extremely old, and so has many craters - including the planet's largest, 1,400-mile-wide (2,300 km) Hellas Planitia - while that of northern hemisphere is younger and so has fewer craters. The number of craters on Mars varies dramatically from place to place, depending on how old the surface is. This difference between the north and south might be due to a very large impact shortly after the birth of Mars. The northern hemisphere mostly lies at a lower elevation than the southern hemisphere, suggesting the crust may be thinner in the north than in the south. The lowest of the northern plains are among the flattest, smoothest places in the solar system, potentially created by water that once flowed across the Martian surface. Many regions of Mars are flat, low-lying plains.
However, the amount of oxygen depends on temperature and pressure temperature changes on Mars from time to time as the tilt of its rotation axis shifts. A study by scientists in 2018 suggested that salty water below the Martian surface could hold a considerable amount of oxygen, which could support microbial life. Water may still lie in cracks and pores in underground rock. Some channels can be 60 miles (100 km) wide and 1,200 miles (2,000 km) long. (Image credit: NASA/JPL)Ĭhannels, valleys and gullies are found all over Mars, and suggest that liquid water might have flowed across the planet's surface in recent times. The solar system's largest volcano, Mars' Olympus Mons, seen by NASA's Viking 1 mission. Some minor eruptions might still occur on the planet today. Mars also has many other kinds of volcanic landforms, from small, steep-sided cones to enormous plains coated in hardened lava. Olympus Mons is a shield volcano, with slopes that rise gradually like those of Hawaiian volcanoes, and was created by eruptions of lava that flowed for long distances before solidifying. The massive volcano, which is about 370 miles (600 km) in diameter, is wide enough to cover the state of New Mexico. Mars also has the largest volcanoes in the solar system, Olympus Mons being one of them. Large channels emerging from the ends of some canyons and layered sediments within suggest that the canyons might once have been filled with liquid water. The canyons merge in the central part of the Valles Marineris in a region as much as 370 miles (600 km) wide. Individual canyons within the system are as much as 60 miles (100 km) wide. Scientists think the Valles Marineris formed mostly by rifting of the crust as it got stretched.
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