The European Space Agency (ESA) probe found enough water to cover the planet's surface Mars It's about 4.9 to 8.9 feet (1.5 to 2.7 meters) deep, buried in dusty ice beneath the planet's equator.
The discovery was made by the European Space Agency's Mars Express mission, a veteran spacecraft that has been involved in science operations around Mars for 20 years now. While this is not the first time evidence of ice has been found near the Red Planet's equator, this new discovery is by far the largest amount of water ice discovered there to date and appears to match previous discoveries of frozen water on Mars.
“It is exciting that the radar signals match what we expect to see from ice sheets and are similar to the signals we see from the polar caps of Mars, which we know are very rich in ice,” said lead researcher Thomas Watters of the Smithsonian Institution at the Smithsonian Institution. United States in a statement to the European Space Agency.
The deposits are thick, extending 3.7 kilometers (2.3) miles underground, and topped by a crust of hardened ash and dry dust hundreds of meters thick. Ice is not a pure mass but is heavily contaminated with dust. While its location near the equator is an easily accessible location for future manned missions, its burial so deep means access to water ice will be difficult.
Related: The Mars Express spacecraft reports evidence of ancient microbial, water and volcanic life on the Red Planet
About 15 years ago, Mars Express discovered sediments beneath a geological formation called the Medusae Fossae Formation (MFF), but scientists weren't sure what these sediments were made of. Mars' geography is divided between the northern highlands and the southern lowlands, and the massive 5,000-kilometre-long MMF lies near the border between the two.
The MMF itself is suspected to have formed over the past 3 billion years from lava flows and was covered in volcanic ash during an ancient era when Mars was volcanically active. Today, MMF is Covered in piles of dust Several kilometers high, it is actually the most abundant source of dust on the entire planet, and fuel for this giant Sand Storms Which could engulf Mars on a seasonal basis. Were the sediments just dust, perhaps filling a deep valley?
New observations made by MARSIS, an underground radar aboard Mars Express, now have the answer — and it's not dust.
“Given how deep it is, if the MFF were just a giant pile of dust, we would expect it to become compact under its own weight,” Andrea Cicchetti of the National Institute of Astrophysics in Italy said in a press release. “This would create something much denser than what we already see with Mars.”
Instead, the sediments are low-density and fairly transparent to the MARSIS radar, which is exactly what one would expect for water ice to appear in the data.
More relevant is the question of how water ice is buried at the equator. Subsurface ice has been found in abundant quantities on Mars before; NASA's Phoenix mission drilled ice just beneath the dusty surface at the rover's polar landing site in 2008. Meanwhile, early in its mission, Mars Express discovered abundant water ice extending into the mid-latitudes, and a NASA team also discovered abundant water ice extending to middle latitudes. Odyssey of Mars Evidence of water was even found in MMF in 2009.
More recently, the European Space Agency Track the gas orbit Hydrogen was discovered from water ice below the surface of the Candor Chaos, part of a massive tear in the surface of Mars that we call Vallis Marineris. In addition, they are called the remains of ancient glaciers Glacier remainsIt was spotted in Sharqia Noctis Mazewhich is located 7.3 degrees south of the equator.
The presence of subsurface water ice at low and tropical latitudes indicates how the climate of Mars was very different in the distant past.
“This latest analysis challenges our understanding of the MFF and raises as many questions as answers,” Colin Wilson, an ESA project scientist for Mars Express and Trace Gas Orbiter, said in the statement. “How long ago did these icy deposits form, and what did Mars look like at that time?”
The presence of ice could be a result of Mars' wandering axis. Throughout the Red Planet's history, the axial tilt of the planet's poles is understood to have changed quite chaotically. Currently, Mars' poles are tilted toward the ecliptic by 25 degrees (compared to Earth, which has a tilt of 23 degrees) but in the past this could range from as shallow as 10 degrees, to as extreme as 60 degrees. .
During periods of high inclination, when the poles are closer to the Sun than the equator, water ice can form in large quantities on the surface at the equator. This ice could then be buried by falling ash and dust, remaining covered to this day.
The changing tilt could also explain the 400,000-year-old features It was discovered on Mars by the Chinese Zhurong roverAnd also Presence of grooves It consists of liquid water where such water should not exist.
The new discovery is described in a paper published in the journal Geophysical Research Letters.
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