NASA’s Curiosity rover is preparing to send its powerful impact drill through the surface of Mars for the first time, targeting a rocky outcrop fractured by vein-like channels– channels that probably once held water.
“What these vein fills tell us is water percolated through these rocks,” said project scientist John Grotzinger, of the California Institute of Technology in Pasadena. “[Water percolated] through these fracture networks and then minerals precipitated to form the white material that ChemCam (a rover instrument) has concluded is very likely a calcium sulfate, probably hydrated in origin.”
The researchers reached their conclusions based on comparing the Martian rocks to known samples from our own planet. “On Earth, usually, these veins are formed by water circulation in fractures, and this usually occurs in low to moderate temperatures,” said ChemCam team member Nicolas Mangold of the Laboratoire de Planetologie et Geodynamique de Nantes, France.
The rover has also observed several small spherules, or concretions, which strongly indicate the historical presence of water on Mars’ surface. Additionally, the rocks could provide NASA with clues to how materials like water are transferred through the planet’s surface layers.
“All of these are sedimentary rocks, telling us Mars had environments actively depositing material here,” said Aileen Yingst of the Planetary Science Institute in Tucson, Arizona. “The different grain sizes tell us about different transport conditions.”
Since landing on Mars in August, the Curiosity rover has been diligently searching for signs that the planet offered a favorable environment for microbial life. Previous orbital observations of Gale Crater, in which the spacecraft landed, suggested that the rocky area likely held surface water at one point.
“We will go into the sequence of rocks that are the brightest prospects for telling us about the early habitability of Mars,” said Grotzinger. “We are at a very sweet spot to do that.”
Rocks in the area are sandstone, according to NASA geologists, while others nearby are siltstone, consisting of very fine grains. The drill site, named after the late Mars Science Laboratory deputy project manager John W. Klein, is cut through with veins that the rover’s ChemCam laser spectrometer indicates hold precipitated minerals – most likely hydrated calcium sulphate, possibly bassinite or gypsum.
So far, the rover has focused on taking pictures and conducting surface analysis. Since arriving in August, the craft has transmitted 18,226 images and nearly 10 gigabytes of raw information about the planet’s geology, mineral chemistry, soil composition, and atmosphere. The next task, drilling and collecting rock dust, represents the most complex undertaking yet for NASA’s engineers.
“Drilling into a rock to collect a sample will be this mission’s most challenging activity since the landing. It has never been done on Mars,” said Mars Science Laboratory project manager Richard Cook of NASA’s Jet Propulsion Laboratory in Pasadena, California. “The drill hardware interacts energetically with Martian material we don’t control. We won’t be surprised if some steps in the process don’t go exactly as planned the first time through.”
The rover’s drill is designed to penetrate about 2 inches into the Red Planet’s subsurface to extract a small portion of powdered rock, which will then be analyzed using an onboard chemistry kit. Curiosity’s team anticipates that the process will require six weeks or more. Extreme caution is necessary in an environment where repairs and replacement parts are hard to come by. Among NASA’s concerns are that the Martian rock might damage the drill bit, or that the mineral sample will be contaminated by remnants of the machine’s Earthly origins as the rover scoops it onboard.
After traveling 352 million miles to reach its destination, it may at first seem like the rover is making slow progress across the Red Planet’s surface, covering 100-150 meters on a good day. However, the mission has already generated some very interesting findings. Earlier this month the rover’s Mars Hand Lens Imager (MAHLI) examined sedimentary rocks in Yellowknife Bay, where it currently resides, identifying rock deposits that were laid down in a streambed billions of years ago.
“Scientifically, it is fantastic,” said NASA planetary soil scientist Doug Ming at the Johnson Space Center in Texas.
As the rover uses its drill for the first time in the coming days to open the veins of Mars, it is sure to unlock further secrets from the Red Planet’s mysterious past. Given the recent evidence of surface water, perhaps one of these days Curiosity’s drill will hit the jackpot: fossilized evidence of microbial life.