Curiosity Finds Martian Rock Similar to Rare Earth Rocks

After analyzing soil and rock samples collected on Mars by the Curiosity rover, scientists have discovered the Red Planet has a type of rock that's unlike most known Martian rocks, yet surprisingly similar to a rare type of oceanic rock found on Earth.

The Martian igneous rock was examined by the rover's extensive suite of instruments, revealing new information that leads scientists to believe that Mars may be more like Earth than we ever knew.

The researchers report their findings in the journal Science. A separate study also published this week revealed that the Martian soil is 2 percent water by weight.

"The results presented go beyond the question of habitability," said John Grotzinger, a project scientist at the Mars Science Laboratory (MSL) and geology professor at Caltech. "Mars Science Laboratory also has a major mission objective to explore and characterize the geological environment at all scales and also the atmosphere. In doing this we learn about the fundamental physical and chemical properties that distinguish the terrestrial planets from each other and also what they share in common."

The rock in question, a 50 centimeter-tall, pyramid-shaped rock, was spotted on the Martian surface in first days of the Curiosity expedition, which is now in its 14th month. Scientists named it Jake_M, after MSL surface operations systems chief engineer Jacob "Jake" Matijevic, who died two weeks after Curiosity's landing.

Scientists suspected Jake_M to be a fine-grained basaltic igneous rock formed by the crystallization of magma near the planet's surface. The lack of mineral grains on the rock's dust-free surface hinted that it would have a relatively uniform chemical composition.

Using the Curiosity's Alpha Particle X-ray Spectrometer and ChemCam, the scientists learned that Jake_M is highly enriched in sodium and potassium, making it chemically alkaline and by comparison dissimilar to other Martian rocks analyzed previously by the Spirit and Opportunity rover programs.

But despite the rock's chemical differences to its Martian brethren, the rock shows remarkable similarity to a rare type of rock found on Earth known as mugearite, an igneous rock typically found on ocean islands and in continental rift zones.

"We realized right away that although nothing like it had ever been found on Mars, Jake_M is similar in composition to terrestrial mugearites, which although uncommon are very well known to igneous petrologists who study volcanic rocks on Earth," said Edward Stolper, a Caltech geology professor and lead study author. "In fact, if this rock were found on Earth, we would be hard pressed, based on its elemental composition, to tell it was not an Earth rock."

However, Stolper adds, "such rocks are so uncommon on Earth that it would be highly unlikely that, if you landed a spacecraft on Earth in a random location, the first rock you encountered within a few hundred meters of your landing site would be an alkaline rock like Jake_M."

Stolper said that although the find is remarkable, it's important not to get carried away. The rock could be a one-off. On the other hand, however, it could also be representative of an important class of igneous rocks from Mars' Gale Crater region. Stolper said finding out the answer will be a key goal of the ongoing MSL mission.