University of Iowa scientist: Solar wind stripped Mars atmosphere

IOWA CITY — Solar winds are not like the gusts, gales, or even squalls we know here on Earth.

At their peak intensity, they can pack the same energy as a million tons of TNT — or a fairly large nuclear weapon — according to Jasper Halekas, an associate professor in physics and astronomy at the University of Iowa.

'And the early sun had a lot more of these extreme space weather events,' Halekas told The Gazette on Thursday following a NASA news conference on early findings from its Mars Atmosphere and Volatile Evolution mission — known as MAVEN.

Halekas, principal investigator of the solar wind ion analyzer instrument aboard MAVEN, spoke at the NASA briefing about how solar wind appears to have affected the atmosphere around Mars and made it was it is today — extremely cold and dry.

'The removal of atmosphere from Mars by episodic extreme events may have been very important over Mars' history, just as a single tsunami can remove a portion of the ocean shore that would have taken millennia to erode by the steady lapping of the tides,' Halekas said.

Mars, billions of year ago, had a much thicker atmosphere that allowed the planet to host running water and even lakes, Halekas said. Today, its atmosphere is less than 1 percent the thickness of Earth's, and the MAVEN mission was launched a year ago to figure out what transformed the Martian climate from wet and warm to cold and dry.

MAVEN's findings, made public for the first time Thursday and appearing in the new issues of the journals Science and Geophysical Research Letters, show erosion of Mars' atmosphere increases greatly during solar storms.

The mission's measurements indicate solar wind strips away gas from the Martian atmosphere at a rate of about 100 grams a second, according to Bruce Jakosky, MAVEN principal investigator from the University of Colorado in Boulder.

'Like the theft of a few coins from a cash register every day, the loss becomes significant over time,' Jakosky said. 'We've seen that the atmospheric erosion increases significantly during solar storms, so we think the loss rate was much higher billions of years ago when the sun was young and more active.'

Researchers on Thursday also reported a series of 'dramatic solar storms' hit Mars in March 2015, accelerating atmospheric loss. As for what this means for Earth, UI professor Halekas said, there is not a direct correlation.

'The Earth has a magnetic field that protects it from the loss processes we are talking about today,' he said. 'So it's not directly applicable to earth … but a lot of those basic physics processes would still apply.'

Looking forward for Mars, Halekas said, solar wind could eventually leave the planet devoid of any atmosphere.

'But the question is whether any atmosphere is being replenished' from potential reservoirs of gas below the Martian surface, Halekas said.

'That is something that deserves more investigation,' he said.

And MAVEN could get that chance, with its mission already extended for another year and researchers hoping it could go for another 10 — at least.

'The spacecraft is healthy and the instruments are all working,' Halekas said. 'And we haven't even been there for a whole Mars year. We haven't been there for one full set of seasons on Mars. This is just a tiny snapshot of what Mars has to offer us.'