Overall, we can match the TES spectra with ground-up basalt, the type of lava found on Earth’s ocean floor, in Hawaii, Iceland, and some places on the continents. Recent analysis of TES data shows the presence of very small amounts of carbonates — minerals that form from the interaction of rock with water. Analysis of soil from the Viking, Pathfinder, and now the Mars Exploration Rover sites reveals the presence of large amounts of sulfur (5 to 10 percent), but we don’t know yet what mineral the sulfur is in.
Unfortunately, none of this helps much with the question of smell. Very small amounts of highly aromatic molecules typically cause odors, and we don’t yet have the ability to detect them in the martian soil. — PHIL CHRISTENSEN, ARIZONA STATE UNIVERSITY