Curiosity’s Hard-Working Year on Mars Pays Off With Amazing Scientific Discoveries
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NASA's Curiosity rover is a gigantic mobile laboratory. During the last year, it has roved over the Martian surface exploring a small section of Gale crater while making huge scientific discoveries.
The rover was built as a data-generating machine. You put rocks, air, and samples in and you get science out. Specifically, Curiosity is searching for signs of ancient habitability and seeking to answer an important question: Could Mars have ever had living organisms crawling over its surface?
Curiosity's science team includes geologists, chemists, physicists, astrobiologists, and countless other researchers. Using the probe's state-of-the-art equipment, they have drilled into Martian rocks, fired lasers and X-rays, baked powdered soil for analysis, and sniffed the atmosphere. Many of these activities had never been done on the Red Planet, or any planet beyond Earth, before. The data received from Curiosity has bolstered the idea that the planet once had water flowing over its surface and was a place where life could have conceivably thrived. It will take many more months and years of exploring to completely tease out all the details but the rover has already exceeded the expectations of its original designers.
When Curiosity landed on Mars in August 2012, no one yet knew what it would find. Here, we take a look at the last year of scientific explorations, how the rover has expanded our knowledge about Mars, and what the future may hold.
Ancient Mars Was Habitable
The most important finding that Curiosity has made so far is that the ancient environment of Mars was habitable. This was literally the result that the rover was built for. After drilling into a rock and analyzing a sample of its interior, Curiosity found that roughly 20 to 30 percent of its composition was smectite minerals.
Smectites are particular minerals that would have formed in the presence of neutral, non-salty water. This indicates a body of water that was so fresh, you basically could have drunk it, said project scientist John Grotzinger during the announcement in March. This contrasts with the findings of previous Mars rovers, which found jarosite minerals that could have only formed in highly acidic or salty water.
Curiosity also found that the interior of Mars rocks contained sulfur minerals from which microbes could have derived energy. While the discoveries don't say for sure whether or not life existed billions of years ago on Mars, they provide very tantalizing evidence. Hopefully, further data will provide even better confirmation of Mars' ancient habitability.
Image: Grey-green unoxidized powder from the interior of a Martian rock that helped determine the composition of the planet billions of years ago. NASA/JPL-Caltech/MSSS
Water Flowed Over the Surface
Curiosity had barely roved anywhere on Mars when it stumbled right into an ancient riverbed. This area, nicknamed Yellowknife Bay, sits at the bottom an an alluvial fan, where a watershed could have flowed billions of years ago, distributing rocky debris. Though there had been evidence of this finding from pictures taken by orbiters, Curiosity provided the ground-truth results confirming that Gale crater had a wet past.
Scientists working with Curiosity think the area could have once been a fast-moving river that may have been ankle- or even hip-deep on a person standing there. Tiny rocks called clasts had accumulated in Yellowknife, sticking together to form a larger composite rock. The clasts were rounded, suggesting that they had been weathered and transported a long distance, most likely by water because they were too large for wind to have picked them up.
Further exploration at Yellowknife Bay showed evidence that water had percolated through the rocks there, indicating that the environment was dynamic. At certain points in its past the place may have been wet only to dry out later on, and then be filled with water again afterwards. The formations in the image above are fossilized underwater dunes that could have formed at the bottom of an ancient riverbed.
Gale Crater May Contain Simple Organics
A media firestorm erupted in November when Curiosity's project scientist John Grotzinger made a casual comment to a reporter. New data from the rover was going to be big, Grotzinger told NPR's Joe Palca, one for the history books. NASA was forced to backpedal on Grotzinger's tantalizing words, trying to downplay what Curiosity's secret big breakthrough was. But most people expected that the news could only be one thing: Curiosity had found organic carbon on Mars, a potential indication of ancient life.
When the agency finally held a press conference in December, the results were less than impressive. Curiosity had scooped the Martian soil, analyzed it with its internal laboratory, and found evidence for organic compounds. Far from a blockbuster, there-could-have-been-life-on-Mars announcement, the findings were presented in the cautious light of scientific inquiry. Yes, the research team had discovered some carbon. But it was bound in simple compounds that could have easily come from Earthly contamination or been formed during the sample analysis itself.
The finding was less than monumental but showed the science team that Curiosity's instruments worked as expected and would one day be able to deliver a more robust answer. Expectations may have been high but it would have been truly shocking if some random dust scooped from the surface had contained the clues to Mars' living past. In all likelihood, such evidence has disintegrated from the surface and, should it exist, scientists will need to dig deep to find it.
No Martian Methane
In 2009, Earth-based researchers announced that they might have detected large plumes of methane on Mars. The findings raised some eyebrows, mainly because they seemed too good to be true but also because of what they implied. Methane is a simple organic compound that is almost entirely a byproduct of living organisms on Earth. Nearly 99 percent of methane on our planet comes from microbial action and cow farts, and seeing it on Mars raised the hopes of those who think life may still exist on the Red Planet.
Alas, Curiosity has sniffed the Martian atmosphere and turned up methane-free. Though it found certain molecular clues that show Mars would have once had a thicker atmosphere and therefore have been warmer, it has all but crushed the optimistic expectations for finding modern microbes on Mars. But hope remains. The methane on Mars may simply be seasonal, released when the climate is more temperate or other factors are present. Curiosity will continue to periodically test the atmosphere to search for this elusive gas and may one day find something exciting.
Image: Curiosity's Sample Analysis at Mars (SAM) instrument, which analyzed the Martian atmosphere. NASA/JPL-Caltech/MSSS
Radiation en Route to Mars Is Harsh
As it flew through space on the way to Mars, Curiosity measured the levels of radiation. Because it was behind a shield similar to the one that could be used for a manned Mars mission, this data has been eagerly awaited by biomedical researchers. Curiosity showed that the radiation a human crew could expect on the way to and back from Mars would be dangerously high, roughly 13 times the legal limit a person working at a nuclear power plant can receive in a year.
Radiation is already a known problem for deep-space missions. And medical researchers will still debate exactly how much radiation is considered safe. Right now, astronauts are not allowed to be exposed to the levels of radiation that Curiosity measured. But a manned Mars mission will take on more risk than is currently permitted and radiation would simply be part of that. The Inspiration Mars mission, which aims to send a husband and wife team on a round-trip around Mars in 2018, had already been planning for large radiation doses. To minimize health risks, they want to send an older couple that is past child-bearing years. But a future mission would likely need to develop much better shielding techniques in order to keep down the many dangers posed by space-based radiation.
Rocky Diversity on Mars
Scientists chose Gale crater as Curiosity's landing site because they knew it contained a wide variety of different rock types. What they didn't quite expect was to uncover a geologist's dream site so soon after landing. Whereas past Mars rovers have mostly encountered basaltic rocks, Curiosity has seen a large diversity in its year on Mars.
One of the first stones the rover encountered was a highly fractionated alkalic rock, a type never before seen on Mars. Such rocks are familiar on Earth at island chains and rift zones, suggesting that Gale crater has a dynamic geological past. Curiosity's laser and X-ray analyses have also detected other volcanic rocks and its surveys at Yellowknife Bay have found sedimentary rocks galore. And analysis from Curiosity's drillings have uncovered smectite minerals, which provide good evidence for an ancient benign, watery environment.
Image: X-ray diffraction analysis, showing the presence of olivine and feldspar. NASA/JPL-Caltech/Ames
What's That Bright Object?
Though not quite a discovery, photos early in Curiosity's mission showed a bright white object on the sand near the rover. Scientists were baffled and the public, as always, was excited at the prospect of a mystery. Curiosity's research team was mainly interested in identifying the material so as to make sure it wouldn't contaminate their first efforts to scoop the Martian soil.
The unexpected object was eventually determined to be a piece of plastic that fell from the rover. Similar loose screws and other bits have fallen from previous rovers. After figuring that the bright object was not harmful, the science team went back to their normal operations. The scooping was briefly interrupted again when images showed another fleck of white something thought to be a Martian mineral (the researchers referred to it simply as "shmutz") but that, too, was determined to be non-problematic.
What the Future Holds
With a year under its belt, Curiosity is now off to conduct major explorations at the foot of Mount Sharp, the 5-kilometer-high peak at the center of Gale crater. The rover will climb this mountain, watching as the layers of Martian history reveal how the planet changed from wet to dry over billions of years. As long as nothing goes wrong, who knows what new discoveries it might make? Considering that its nuclear battery could last 14 years, though, there will certainly be a great deal of new findings and exciting surprises.
Curiosity is likely to rove by a few known areas of interest. Perhaps the science team will find a fairly recent crater that has punctured a hole deep into the Martian interior, giving them a good look at the Red Planet's past. There is also a strange formation ahead of the rover, a gigantic network of fractures that formed when geological processes broke up Mars' crust (seen above). In the intervening time, interesting minerals may have filled these rectangular crevices, allowing for intriguing new discoveries. Curiosity is also likely to encounter phyllosilicates at the base of Mount Sharp. These minerals formed in the presence of water and are also good at sequestering organic carbon. There is a chance Curiosity will be able to figure out a lot about Mars' ancient habitability by analyzing such rocks.
Image: Strange fractures near the base of Mount Sharp. NASA/JPL-Caltech/Univ. of Arizona