Mars is commonly regarded as the Red Planet because of the abundance of iron oxide on its surface. However, NASA’s Curiosity rover recently drilled a small hole that revealed that below the planet's rusty shell, where the rock is protected from the elements, is a slate-blue interior. Analysis of the drilled sample will help scientists understand how the Martian environment changed over time, going from a planet that held vast oceans to a dry and barren landscape.
Curiosity drilled the hole at Telegraph Peak on February 24. This was the third drill site in the rover’s five-month-long mission at Pahrump Hills, near the base of Mount Sharp. The two previous drilling locations also yielded grayish-blue soil under the red surface.
"This was our first use of low-percussion drilling on Mars, designed to reduce the energy we impart to the rock," John Michael Morookian of Jet Propulsion Laboratory said in a February press release at the beginning of the Pahrump Hills mission. "Curiosity's drill is essentially a hammer and chisel, and this gives us a way not to hammer as hard."
The rover drilled a hole, with a circumference about the size of a dime, utilizing the same technique as with other locations in the Pahrump Hills region. The success of those previous drill sites gave the crew the confidence to proceed drilling at Telegraph Peak, even without a preliminary drilling test to ensure conditions were favorable. This is the first time in over two years that Curiosity has drilled a sample without first completing this test.
The rock sample, which had been pulverized into a powder, was then analyzed using Curiosity’s Alpha Particle X-ray Spectrometer (APXS), ChemCam, and Chemistry and Mineralogy X-Ray Diffraction (CheMin) spectrometry instruments in order to determine the soil’s composition. It was revealed that the Telegraph Peak sample had a higher ratio of silicon to aluminum and magnesium than the samples from the other Pahrump Hills sites.
"When you graph the ratios of silica to magnesium and silica to aluminum, 'Telegraph Peak' is toward the end of the range we've seen,” Doug Ming from NASA’s Johnson Space Center said in a press release. "It's what you would expect if there has been some acidic leaching. We want to see what minerals are present where we found this chemistry.”
Prior to Curiosity’s arrival at the base of Mount Sharp in September of 2014, the rover had been exploring the rest of Gale crater. Mount Sharp, officially called Aeolis Mons, is in the center of the crater. It has been a long-term goal of the mission for the rover to drill and analyze rock samples from this location.
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