Today at Brown

On July 15, 1965, the Mariner 4 spacecraft returned the first image of Mars to the world. A television camera on board snapped a black and white photograph that showed wispy bands of white against a gray, arcing backdrop — but at such low resolution that scientists could only guess whether some of the haze-like features were clouds.

Now more than a dozen missions later, the world has seen dramatic shots of the Red Planet taken by instruments so sophisticated they can “see” Mars across the electromagnetic spectrum. Thanks to a wealth of new information, scientists can say with a great deal of confidence that water has existed on Mars in some form — and likely in great quantities and across vast areas.

But despite those advances, the instruments can’t agree on the depth at which water was present on Mars, and that has left scientists guessing whether water played a major role in chemically changing the planet’s surface or was mostly a bystander.

The data “leave us with some major gaps,” said Michael Wyatt, assistant professor of geological sciences at Brown, “so we have more work to do to figure out what’s happened on Mars.”

To get some answers, Wyatt and a team of planetary geologists from Brown have traveled to Iceland.

Iceland may seem a strange choice, but the island nation hugging the Arctic Circle shares many similarities with what scientists think ancient Mars was like, the geologists say. It’s cold and it has water as liquid and as ice — the two states in which scientists believe water existed on Mars. Perhaps most importantly, Iceland has loads of basalt, the most common volcanic rock on Earth and Mars. The scientists will collect cores of basalt and will measure the concentration of silica throughout the core column, which can tip them off whether water was present in the rocks.

The Riddle

The team will try to solve a riddle that has cropped up from data spun off by three instruments that have recently surveyed Mars. The Thermal Emissions Spectrometer was launched in 1996 on board the Mars Global Surveyor. Its goal was to measure the thermal infrared energy (heat) emitted from Mars and to locate minerals, such as silica, in the rocks. TES saw lots of silica at depths of hundreds of microns, or at less than a hundredth of one centimeter.

While planetary geologists hailed the finding, it ignited a debate: Had the silica-enriched rocks been altered by water or were they a different type of igneous rock that had been forced upward from deep within the planet in which water had played no role?

The OMEGA instrument, which rode aboard the European Mars Express mission earlier this decade and operated in the visible and near infrared spectra, penetrated the surface more deeply than TES, to just tens of microns. It, too, failed to solve whether the rocks had been influenced by water or were magma leftovers.

That left the job to the Gamma Ray Spectrometer, which accompanied the 2001 Mars Odyssey mission. The GRS measured mineral content at depths extending to 50 centimeters — much deeper than the two previous instruments. Scientists hoped it would show how deep the enriched silica was present in the rocks. But while TES and OMEGA showed high concentrations of enriched silica in the northern latitudes of Mars, GRS showed nothing.

That really puzzled the scientific community.

The Brown team’s objective is to mimic in Iceland what the instruments have done on Mars. They will travel into the interior of Iceland, a dramatic and tortured terrain dotted with active and dormant volcanoes (see maps) that is considered the Earth’s closest equivalent to the barren northern latitudes of Mars. There, the team will take samples at thermal and near infrared wavelengths, just like the TES and OMEGA instruments. Researchers also will take samples at various depths, extending to 50 centimeters, and bombard them with cosmic rays (through a computerized model), mimicking GRS’s work. They hope that by comparing the results, they can figure out why the instruments are telling different stories.

“We want to go to Iceland and take a block from there and then characterize the chemistry and mineralogy [of the samples],” Wyatt explained. “We’re going to measure how far down alteration takes place.”

The scientists hope their experiments will reveal GRS’s ability to sniff water-altered rocks underneath Mars. If they can conclude water was acting deeply, then it bolsters theories that water played an important — perhaps pivotal — role in the planet’s formation and evolution. If they can determine that water acted exclusively near the surface, that would likely deflate such speculation.

A lot of people will be watching and waiting for the results.