After a 352-million-mile journey, NASA's Curiosity rover touched down on the early morning of Aug. 6, 2012. The fated "Seven Minutes of Terror" had passed, and JPL headquarters received word that Curiosity survived the brutal decent. The rover beamed back images of its shadow on the Martian surface.
In the month that followed, the team performed systems checks to make everything was in working order for the rover's two-year-long mission ahead.
Then the science started. Curiosity—with its multi-billion dollar payload of scientific cameras and lasers—has continued to discover new things about the red planet. It's two-year-mission is a conservative estimate, with the team expecting something closer to three or four years of operation. Here's what we've learned so far.
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The Raging Rivers of Mars
Just 52 days into its mission, Curiosity discovered "tiny rounded pebbles" between the area north of Gale Crater and the foot of Mount Sharp—the rover found an ancient Martian river bed. Project scientist John Grotzinger stated that pebbles like these would've required thousands if not a million years to form. Scientists suspect the river that once flowed here move at 3 feet per second and was anywhere from ankle- to waist-deep.
Signs of (Past) Life?
Drilling into the Red Planet's surface, Curiosity discovered a soup of organic compounds necessary for life. Within the gray rocks, the rover found traces of water, sulfur, and chlorine-containing substances. Curiosity is the first rover able to scoop soil for further examination. The next step for researchers is to find if these compounds are native to Mars. If so, they will share similar isotopic ratios as the Martian atmosphere.
Although this site provided a healthy helping of complex chemistry, the team believes there's more ahead as Curiosity approaches its final destination, Mount Sharp (as the rover has already seen at Yellowknife Bay).
In March, scientists announced that after analyzing the rock sample, they concluded that this area could have once supported life. This area became the first definitive evidence of a habitable environment outside of Earth.
The Situation on Radiation
A collective sigh resounded from aspiring astronauts everywhere when Curiosity discovered that future space-faring explorers wouldn't be immediately eviscerated when stepping into the Martian atmosphere (Good news, everyone!). With no magnetosphere and a super-thin atmosphere, there was a possibility that Mars would be too dangerous for humans to visit, but Curiosity put those fears to rest. "Basically we're finding the Mars atmosphere is acting as a shield for the radiation on the surface," says Don Hassler, principal investigator for the Radiation Assessment Detector.
But the radiation danger, while not as bad as it could be, still lingers. By NASA regulation, astronauts are allowed 1 to 4 Sieverts of exposure to radiation their entire careers. After a 18-month journey and six months on the surface, radiation remains a large problem to overcome if we hope to see humans on Mars. As Hassler says, this has moved the discussion from whether it's possible to stand on Mars' surface at to how long a person could stay.