NASA Curiosity Rover on the Verge of Potentially Historic Discovery: Water on Mars


Astrophysicist Neil deGrasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History, writes (Space Chronicles: Facing the Ultimate Frontier) and speaks about planetary things and makes them come to life for people like me who aren't well-schooled in the sciences ("Can We Make it to Mars?" on NOVA Science/PBS).  

My natural curiosity about things, and being the fortunate and grateful mother of two sons, has resulted in my heightened intrigue about the exploration on Mars.  It is also a nice break from the politics that seem to take precedence over far more interesting subjects that could be reported on.

I wanted to know why it's a huge big deal that we now know that water existed and moved on Mars. Answer: It is the first of three things that must be discovered in order to determine if it was once habitable. But there is so much more to it than that.

For the best, shortest and most scientific explanation of what happened this week, go to the NASA website. For the rookie interpretation, and some additional great links, keep reading. NASA has a fabulous overview video of the Curiosity rover project and has captured an amazingly informative September 27 news conference.

About Mars

Mars is a reddish color because there is lots of iron in the soil and its air made it turn. It was named after the Roman god of war (bloody red). It is fourth closest planet to the sun, has a diameter of 4,200 miles (the Earth's diameter is about 7,920 miles). There are some pretty tall peaks on Mars, including a volcano, Olympus Mons (about 15 miles high) and Mount Sharp (about three miles high). Mount Sharp is located in the Gale Crater, which is 96 miles in diameter and 14,400 feet below Martian "sea level." As with the Earth, Mars's poles are covered in ice that becomes thicker in winter. 

The atmosphere is very thin and the temperature on Mars is very cold. The absolute warmest it ever gets on Mars is about 70-degrees Fahrenheit at noon, and it frequently reaches minus 225 degrees Fahrenheit at the poles. Water is either frozen at the poles or in deep underground springs.  It has a more drastically changing climate than the Earth, although the seasons are similar.  Currently it is winter on Mars and will soon be spring.

Because of the huge temperature difference between day and night, the air is humid at night but dry during the day. Air pressure varies much more on Mars than on Earth because temperatures are so varied and the atmosphere is mostly carbon dioxide on Mars. Winds on Mars can be very strong, creating dust storms that take months to settle.  

Mars topography includes an alluvial fan where debris spreads out as it is going down a slope. Here on Earth, these fans are formed by water flowing down a steep canyon and can be observed in Death Valley, between Los Angeles and Las Vegas. Curiosity has found rounded pebbles in these rocky areas, evidence that water flowed there to create the fan.  Water carried the pebbles down the slope in the fan pattern to where Curiosity currently sits. The size and shape of the stones give scientists clues about the speed and distance of the stream that flowed. Because there are many channels in the fan, it appears water flowed over a long time. It "could be easily thousands to millions of years," according to Bill Dietrich of the University of California, Berkley, at the news conference.

Video about the Mars Streambed

Video comparing Earth and Mars River Fans

Curiosity and the Gale Crater

On November 26, 2011, the Atlas V rocket carrying NASA's Mars Science Lab spacecraft and the Mars rover Curiosity launched from Cape Canaveral Air Force Station in Florida. The spaceship reached Martian atmosphere, released the Mars Science Laboratory, and it landed safely on the surface of the planet in the Gale Crater on August 5, 2012. Currently, it is winter on Mars, nearing the beginning of spring.

Gale crater offers a thick packet of sediment, rocks and minerals that can help determine the secrets of its past. Curiosity will cover a distance of 12 miles or more during its mission. To "explore for and find habitable environments" is the "core of its mission," as defined by John Grotzinger, the project scientist, at the September 27 news conference.

Next for Curiosity will be more movement toward its destination, a site called Glenelg, at the slope of Mount Sharp, and using its robot arm for the first time. The rover will "scoop" materials in the arm and park for 2-3 weeks to get sediment samples. Later it will drill for rock samples at Glenelg.

Aside from the rather amazing landing, called "seven minutes of terror," the pre-landing maps and views from the constantly orbiting crafts have provided scientists with photographs, measurements and visual information that helped define the surface and cause them to speculate about the meaning of the "fans," as seen from above the planet. Now the hypotheses that water once flowed have been determined by clear evidence of multiple streams, running for a long period of time. 

"A long-flowing stream can be a habitable environment," says Grotzinger. "It is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."

The three things scientists look for to determine a habitable environment are: "Water; sources of energy for microorganisms to utilize their metabolism and source of carbon to build structures," said Grotzinger. Now, "we've got the hall pass for the water observations."

In the months to come, many are eagerly awaiting the findings that could identify energy sources for microorganisms and sources of carbon, the final two checkpoints needed to determine habitability of Mars. 

Curiosity's mission is expected to be about two years. Was Mars once habitable? We don't know yet. Finding conclusive evidence of water is the first big step toward that discovery.

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