Mars rocks Darby Dyar, visiting assistant professor of geology, holds sample cases containing pieces of meteorites that fell to Earth from Mars. Her analysis of the tiny pieces may yield information about how entire planets evolved. Photo by Fred LeBlanc.
"Of the thirteen known Martian meteorites, pieces of five are here at Mount Holyoke," Dyar says, noting that they're securely stored in an undisclosed location. Four of the samples were among the thousands of rocks collected by scientists in Antarctica, where thick ice means that any rocks on the surface fell from the sky. "People have collected meteorites from Antarctica for many years," Dyar explains, "But it wasn't until the early 1980s that they realized that some came from Mars."
A glasslike layer reveals some rocks' extraterrestrial origin, as speeding through Earth's atmosphere melts, then cools, the rock's outer layer. And their Martian origin is confirmed by the composition of gases trapped inside the meteorites like air pockets in a loaf of bread.
Martian rocks contain many minerals common on Earth, such as pyroxene, feldspar, and olivine, which leads Dyar to believe that "Earth and Mars formed by similar processes." However, she feels there's only "a remote possibility" that life ever existed on Mars. She has part of the Martian rock (right) that caused a furor a few years back when scientists claimed to have discovered bacterial life in its furrows. Dyar believes what they saw either wasn't biological or wasn't from Mars.
Dyar studied moon rock samples for her doctoral dissertation at MIT, and her grand plan is to compare the geology of Earth and Mars rocks with asteroids and rocks from the Moon. "It's great to hold a lunar rock in your hand because you can look at the moon and see where it comes from, but Mars rocks are even cooler," the enthusiastic geologist tells a prospective student who happened by her office.
As one of the world's foremost experts in analyzing the iron content of rocks, Dyar won a National Science Foundation grant to analyze the iron in related samples from the Earth's interior, which she will contrast with minerals in these meteorites. This, in turn, will reveal information about the oxygen composition of Mars as it evolved. From there, Dyar will form conclusions about the atmospheric evolution of the planet. "From these little rocks, we're deducing how entire planets evolved," she explains. "That's the name of the game."
The game will get even more interesting in 2008, when the first fresh Martian samples will be brought back to Earth. NASA gets the samples first, and Dyar hopes to get them next.
Competition for Martian samples is extremely tight, since there are many interested scientists and only thirteen rocks are known to have fallen to Earth from Mars. Even the lucky researchers usually get only thin cross-sections to work with. Dyar has chunks. This allows her to test the samples using two different methods.
Working with her are senior honors thesis candidates Maria Stefanis and Desiree Polyak. Are they as excited as Dyar about working on Mars rocks? They're over the moon.
![[Index]](../index3.gif){kind=small}