Lab takes rocky road to Mars research

by Peter Kauffner

Mars may seem as far away as graduation, but there are actually pieces of Martian rock kept at the University’s Lunar and Meteorite Lab in Shepherd Laboratories.
“We have thumbnail-sized pieces of a couple Martian meteorites,” said Robert Pepin, director of the lab and a professor of physics and astronomy.
The lab is funded by a $180,000 grant from the National Aeronautics and Space Administration. NASA has funded the University’s lunar rock research since 1968. The lab’s research is focused on reconstructing the story of how planets developed, especially the history of planetary atmospheres.
“I came here in 1965 and they were already gearing up to receive samples from the moon. (The lab) was established in 1968, just in time for the first samples from the moon,” Pepin added.
Research done at the lab now plays a key role in the debate over whether life existed on ancient Mars.
“We worked a lot on those (Martian) meteorites 10 years ago and helped to establish that they actually did come from Mars,” Pepin said.
Most meteorites were formed when the solar system was created about 4.5 billion years ago. These meteorites were the remnants of planetary formation. However, scientists noticed that half a dozen meteorites were unusually young.
“Young in this context means a billion or two billion years old,” Pepin said.
One of these meteorites, discovered in 1979 in Antarctica, was found to contain gas with a composition similar to that of the Martian atmosphere.
“We found that the gases trapped in this rock were just a dead ringer for the Martian atmosphere composition, which had been measured by the Viking space probe. That remains the greatest single piece of evidence that these things actually came from Mars,” Pepin said.
Despite the excitement and controversy surrounding the Martian meteorites, the focus of the lab’s work remains the lunar rock samples brought back by the Apollo space missions.
“We have a collection of two or three hundred samples from the moon,” Pepin said.
Streams of gas, called solar wind, emanate from the sun. Because the surface of the moon is unprotected by any atmosphere, the solar wind directly strikes rocks on the lunar surface. Over time, solar wind material becomes implanted in the outer layers of lunar rocks.
“The best clue we have as to what was around in the early history of the solar system is from the solar wind,” Pepin said.
Most of the lab’s day-to-day experimental work consists of using acid to carefully peel off the outer layers of lunar rocks. This is done to analyze the composition of the implanted solar wind particles.
“We haven’t yet got a satellite out into the solar wind so that we can actually measure its composition directly,” Pepin said.
The lab also investigates meteorites, which it obtains from museums and private sources.
“We had a Wisconsin farmer here earlier today who has what he thinks is a meteorite, but I don’t think it is,” Pepin said.
Although there are private companies that sell meteorite samples commercially, investigators generally rely on museums to provide them with the samples they need.
“(For many museums) all you do is write to the curators, tell them what you want to do and how much you will need, and they will send it to you free of charge,” Pepin said.
Most meteorites were formed even earlier than the planets were, so their composition reflects conditions that existed at that time.
“The overriding research goal is try to figure out how these three planets — Earth, Venus and Mars — wound up with such tremendously different atmospheres today when they presumably all started off from more or less the same feedstock,” Pepin said.