SIU Geologist and the Study of Martian Rocks
March 14, 2016
Earth and Mars are in the same galactic family, made of much of the same stuff and living in – at least in astronomical terms – the same neighborhood. They’re practically cousins. So if you want to know something about one of them, you can look at the other to get a hint at what they’re like.
Of course, we know quite a bit about Earth. We live here. But Mars is a bit harder to get to know. We’ve sent many probes there that have relayed valuable data, but none have returned with physical specimens.
It turns out, however, that Mars has been sending us messages all along, via one of the more violent events that happen in our solar system. And scientists, such as SIU’s Justin Filiberto, are in the business of reading those messages and telling us what they mean.
Filiberto has built his career on the study of Mars rocks. The tiny shards of rock he buys from meteorite dealers got to Earth in a most unconventional way – as debris blasted into space by sheer force of meteorite collisions on the red planet that eventually find their way to Earth as meteorites themselves.
“Meteorites from Mars are rare, yes. There are only about 80 known,” said Filiberto, assistant professor geology. “But they’ve fallen all over the world. We can tell by their geochemistry, which perfectly matches the Martian atmosphere, that they are from Mars.”
Filiberto began working on Mars rocks for his doctorate. He then worked as a research scientist for the Lunar and Planetary Institute, a NASA contractor, before coming to SIU in 2011.
The Mars meteorites have been found on Earth as far back as the 1800s, but back then all scientists knew was that they were very different from terrestrial rocks. No one yet knew where they were from.
It wasn’t until the Viking missions landed on Mars in the 1970s, followed by data analysis in the 1980s, that researchers positively identified their origins by the amounts of nitrogen, carbon and noble gases trapped in the tiny shock melt pockets that punctuate their surface.
“Every planet has a different atmosphere chemistry, so we can pinpoint where rocks come from,” Filiberto said.
The ongoing Curiosity mission to Mars recently prompted NASA officials to unequivocally state they had found evidence of water there. But the question on Filiberto’s mind these days is what that water is like, and might it be suitable for life as we know it.
“If you look at Mars there is lots of evidence for flowing water in the past; but it’s not there now,” he said, adding that NASA has been able to discover that water that was there was very rich in chlorine.
“We know there was water, but what was its chemistry? Was it habitable, or so chlorine-rich that it is not very habitable? Or is it sulfur-rich, which can be even worse for life.”
To answer such questions, Filiberto looks to Earth as an “analog” or baseline guide, for comparing the rocks from Mars to similar terrestrial rocks.
“We know more about Earth than any other planet, so we always come back to Earth as our comparison point,” he said. “We know what happens on the Earth and that there’s life here. We know the types of volcanoes and how they formed here. So when we have rock from Mars, we use earth as comparison so find out how it formed”
Specifically, Filiberto looks at the minerals apatite and amphibole. The hydrous minerals contain water in their crystal structure, which allows Filiberto to compare the amount of water, fluorine and chlorine contained in the crystals of Mars rocks to the same minerals in Earth rocks.
Ultimately, the comparison might tell scientists more about the question of whether life does or has ever existed on Mars by saying something about the water content of its magma.
“This kind of work can tell us how much water was inside the interior of Mars,” he said. “The reason we’re looking at water in the first place is the question of life. If we think there was potential for life on Mars then it probably has to do with water coming out of its volcanoes. On Earth, for instance, the water that degasses from volcanoes is habitable. Might the same be true for Mars?
“We can’t say if anything lived there (on Mars), but we can say whether the chemistry and temperature might have been suitable for life.”
Filiberto will pursue that line of inquiry further this spring with a $20,000 grant from National Geographic to examine sulfur-rich areas in Utah that are analogues to Mars.
“Mars has a very sulfur-rich crust. Earth does not, except in a few weird places,” Filiberto said. The Colorado Plateau in Utah is one such area, and Filiberto, along with Sally Potter-McIntyre, assistant professor of geology, and doctoral student Jake Crandall will head there in May to study it.
The group will be looking at the area’s igneous rocks, the sulfur-rich crust and the areas where the hot, freshly formed igneous rocks came into contact with the sulfur-rich crust and baked and changed the sulfur-rich rocks.
“That’s what we would have expected to see on Mars early in its history,” Filiberto explained. “So we will look at mineralogy and also the biosignatures and isotopic evidence of life to see if we can find evidence of critters living there. Because again, if life existed in these weird zones on Earth, than maybe it could have on Mars, too.”