Most of Mars’ atmosphere was lost to space: NASA

This low-angle self-portrait of Nasa's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin" on lower Mount Sharp. (Nasa FIle Photo)

Solar wind and radiation were responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, new results from NASA have revealed.

“We’ve determined that most of the gas ever present in the Mars atmosphere has been lost to space,” said Bruce Jakosky, principal investigator for the Mars Atmosphere and Volatile Evolution Mission (MAVEN), University of Colorado in Boulder.

The findings showcased that about 65% of the argon (a noble gas which is the third-most abundant gas in the Earth’s atmosphere) that was ever in the atmosphere has been lost to space.

CO2 is of interest because it is the major constituent of Mars’ atmosphere and because it’s an efficient greenhouse gas that can retain heat and warm the planet.

“We determined that the majority of the planet’s CO2 was also lost to space by sputtering. There are other processes that can remove CO2, so this gives the minimum amount of CO2 that’s been lost to space, explained Jakosky.

Liquid water, essential for life, is not stable on Mars’ surface because the atmosphere is too cold and thin to support it.


However, evidence such as features resembling dry riverbeds and minerals that only form in the presence of liquid water indicates the ancient Martian climate was much different - warm enough for water to flow on the surface for extended periods.

“This discovery is a significant step toward unraveling the mystery of Mars’ past environments,” added Elsayed Talaat, MAVEN programme scientist in a paper to be published in the journal Science.

There are many ways a planet can lose some of its atmosphere.

For example, chemical reactions can lock gas away in surface rocks, or an atmosphere can be eroded by radiation and a stellar wind from a planet’s parent star.

The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate.

The team made its estimate using data from the Martian upper atmosphere, which was collected by MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS).

Algae can survive nearly a year and a half in outer space
The plants returned to Earth after 530 days outside the International Space Station.

Algae from the Arctic Circle are used to tough weather, and it turns out they're also able to survive the extreme conditions of outer space. Two specimens recently spent 16 months on the exterior of the International Space Station and became the first plants to make it through these conditions.


The algae, of the Sphaerocystis species, returned to Earth last June after 530 days on a panel outside the ISS, the Fraunhofer research organization announced last week. The specimens withstood conditions including intense ultraviolet radiation, temperatures ranging from -20°C to 47.2°C, and, of course, the vacuum of space.


That said, this all occurred in ideal conditions. "These algae had been desiccated [dehydrated] before they went into space, and during their time on the ISS they were kept dormant, with no growth, no development and almost no metabolism," René Demets of the European Space Agency toldNew Scientist. "But the experiment shows that some terrestrial organisms are robust enough to cope with months of exposure to open space conditions without a spacesuit."

Within days of returning, the algae began behaving normally again, but researchers have yet to examine potential damage to the algal DNA. As New Scientist notes, the survival of the algae adds credence to the "panspermia"theory, which suggests that comets and meteorites can bring life to sterile planets. It also provides insight into whether humans could transport plants to grow on other planets.