Mars meteor shower would have been ‘truly stunning’

IOWA CITY - When a rare Oort Cloud comet last month passed closer to Mars than any previously known flyby, NASA happened to have several instruments on or near the red planet, allowing researchers to capture images and measurements that produced a 'treasure trove” of data.

Two of the instruments advantageously stationed for the once-in-an-8-million-year opportunity involve the work of University of Iowa scientists Don Gurnett, an astronomy and astrophysics professor, and Jasper Halekas, associate professor in the UI Department of Physics and Astronomy.

Gurnett, lead investigator for the MARSIS ionosphere sounding instrument on Mars Express, joined several researchers Friday in presenting findings on the comet, named Siding Spring after it was discovered Jan. 3, 2013, at Siding Spring Observatory in Australia.

'This has been a tremendous event,” said Jim Green, an Iowa native, UI alumnus, and director of NASA's planetary science division. 'Siding Spring has one thing in common with other comets we've seen. It surprised us.”

In anticipation of the historic flyby on Oct. 19, scientists did a 'fair amount of modeling” and determined the comet's dust tail would miss Mars in a 'significant way,” according to Green. But Siding Spring's dust tail was larger than anticipated, and it wasn't positioned as expected.

'The surprise was that we ended up with a lot more dust than we ever anticipated,” Green said.

And it wasn't just any dust.

'The comet's dust slammed into the atmosphere and literally changed the chemistry,” he said.

Siding Spring, which might contain material from the formation of the solar system some 4.6 billion years ago, came within about 87,000 miles of Mars at its closest approach. The result was a meteor shower unprecedented in modern research, according to Gurnett.

'We got our data analyzed pretty quickly and came to the conclusion that it was meteors,” Gurnett said.

Even though scientists weren't anticipating such a profound event, before the comet's arrival, NASA moved its instruments to the other side of the planet and turned them off - just to be safe. Had they not done that, experts said, the spacecraft easily could have been destroyed.

'I think we all breathed a sigh of relief when the signal came back on,” Gurnett said.

Nick Schneider, associate professor in the Department of Astrophysical and Planetary Sciences at the University of Colorado, said that before researchers turned off their instruments they wondered if they'd see any change at all in their data when they turned them back on.

'We were all leaning into our screens to see what we would see,” he said. 'Then we were all pressed back in our chairs at what we did see.”

Chemical changes in the Martian atmosphere included ionized magnesium and iron - not necessarily the atmospheric ingredients they'd expect from comet dust.

The resulting meteor shower - or storm - would have been 'spectacular” to see from the surface of Mars, Schneider said.

'It would have been truly stunning to the human eye,” he said, adding that an astronaut might have been the 'most sensitive instrument of all” to observe the event. 'To have a human see millions of shooting stars happening at once would have been really mind blowing.”

Alan Delamere, an investigator with Delamere Support Services in Boulder, Colo., said much of the data collected during the Mars flyby will take further analysis and could shed light on some mysteries around the dynamics of the solar system.

'We have a comet here behaving quite differently from our previous expectations,” Delamere said. 'All of this is going to involve a lot of intense debate in the coming months.”