Interstellar Clouds Eroded Martian Atmosphere

Solar wind stripping Martian atmosphere
An artist's impression of solar wind stripping the Martian atmosphere. (Image credit: NASA Goddard Space Flight Center Scientific Visualization Studio)

A long time ago, Mars had an atmosphere thick enough to allow running water on its surface. But today these vast gullies — and features that some scientists interpret as ocean shorelines — are bone-dry.

Something thinned the Red Planet's atmosphere over time, and there's a mission in orbit to find out how, when it happened and how quickly.

New results based on observations from MAVEN (Mars Atmosphere and Volatile EvolutioN Mission) have found a possible new source for losing the atmosphere. For years, scientists have known that the solar wind — that stream of charged particles coming from the sun — can strip away hydrogen molecules on Mars. The new study suggests that interstellar clouds are also partially responsible.

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"MAVEN made it clear that ionizing radiation from the sun is the main driver as we it see now. I agree with those results 100 person, and am looking at geological timescales where encounters with interstellar clouds also becomes important," said lead author Dimitra Atri, of the Blue Marble Space Institute of Science, in an email interview with Discovery News.

The changes come as our solar system moves around the galaxy, Atri explained. From time to time, we move through interstellar clouds — vast, dense clouds of gas and dust — in events that last for about a million years. This has happened at least 135 times since the solar system was formed 4.5 billion years ago, Earth's geological records suggest. Each time, the gas and dust in the cloud strike the solar wind and create a bow shock. This shock accelerates charged particles (protons), which Atri suggests will make Mars lose 0.5 percent of its atmosphere each time.

Artist's impression of the MAVEN (Mars Atmosphere and Voltaile EvolutioN Mission) spacecraft orbiting the Red Planet. (Image credit: NASA)

Because each of these events is so long — roughly a million years apiece — Atri's calculations suggest that over time, they contributed to losing half of the Martian atmosphere. Other events attributed to Martian atmosphere loss, such as solar flares and supernovae, have a smaller contribution; Atri says even the strongest solar flare has eight times less magnitude on the escape of the Martian atmosphere than one pass through an interstellar cloud.

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"This study can be extended to other planetary atmospheres as well," he added. "The most important thing I found was the planetary magnetic field. If a planet, like the Earth, has a strong magnetic field, these particles will not be able to penetrate its atmosphere and it will be able to preserve its atmosphere."

Atri hopes to follow up with the research by looking at historical solar events and how they affect the Martian atmosphere. His current study was published in the Monthly Notices of the Royal Astronomical Society.

Originally published on Discovery News.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: