Analyzing the makeup of the rocks, the rover found clay minerals and not too much salt. That tells researchers there once might have been drinkable water on the Red Planet.
"We have found the minerals that we are familiar with as the building blocks of life," May said. "We've also found places that had water, which was a source of energy. There were places where the water was neither too acidic nor too salty. There are areas where the environment would have been habitable billions of years ago. That's probably the biggest things we found."
2.Evidence of ancient water flows: Curiosity found rocks believed to have been smoothed and rounded by ancient water flows. The layers of exposed bedrock tell scientists a story of what was once a steady stream of water flowing about knee deep.
"It is surprising how much water persists under the surface of Mars and how much water must have been there," May said. "What happened? It either went into the rocks or out through the atmosphere."
3. Curiosity detects dangerous levels of radiation: Curiosity detected radiation levels that exceed NASA's career limit for astronauts. With this data in hand, the space agency's engineers can build spacecraft and spacesuits that are able to protect humans on deep space missions.
4. No methane, no life? In September 2013, NASA noted that the rover had not found a single trace of methane in the Martian atmosphere, decreasing the odds that there is life on Mars. Since living organisms, as we know them, produce methane, scientists had been trying to find the substance on the Red Planet, as proof that life might have once existed there. The hunt for methane continues.
5. Significant geological diversity: Scientists were surprised by the variety of soil and rock that they found in the Gale Crater, where Curiosity landed. According to NASA, Curiosity found different types of gravel, streambed deposits, what could possibly be volcanic rock, water-transported sand dunes, mudstones, and cracks filled with mineral veins. All of these yield clues to Mars' past.
Today, Curiosity is closing in on its first good look of its ultimate destination, Mount Sharp.
NASA scientists have wanted Curiosity to study Mount Sharp and its geological layers since the robot landed on Mars Now, the rover is about two miles away and nearing an outcrop of a base layer of the mountain.
"Oh, I think this coming year is going to be even more exciting," said May. "Because we're going to get more detailed stories and compare stratigraphic layers, we're really going to learn about the history of Mars."
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