Wednesday, July 18, 2012

Spacecraft Nears Mars; Landing Just Weeks Away

By Charlene Porter
Staff Writer
Washington - A countdown is on at NASA for the next landing on the surface of Mars, a mission which space agency officials are calling the most challenging and risky undertaking ever made in robotic exploration.
NASA officials briefed reporters July 16 about the landing of Curiosity, the surface craft on board the Mars Science Laboratory (MSL), which left Earth last November. On August 5, MSL will zoom down to the Martian atmosphere at 21,100 kilometers per hour, arriving at a dead stop just seven minutes later, said Doug McCuistion, the director of the Mars Exploration Program. Hundreds of unique events occur in those minutes, he said, and each must be perfectly executed if Curiosity is to land on the selected landing site.
"Every landing is unique, every landing is like a first," said McCuistion. Distinct from the complexity of the landing operation itself, McCuistion said, are the challenges that can arise on Mars, such as unexpected dust storms or density changes in the atmosphere.
NASA engineers say the landing of the unmanned rover craft is the time the mission will encounter the greatest risk. A heat shield must protect the car-sized vehicle from intense temperatures entering the atmosphere. A parachute must slow the powered descent, and then a "sky crane," built into the spacecraft, will deploy to gently lower the rover to the surface. When the spacecraft senses the rover's touchdown, the cable to the descent stage vehicle will sever and that part of the craft will veer off the landing site to descend about 150 meters away.
NASA scientists have targeted Curiosity's landing for a specific location on the Martian surface the team has named Gale Crater. For a few days after landing, the craft will undergo a systems check to insure that all equipment is functioning properly. But it won't be long before the craft sets off in search of answers to the big question.
"Has Mars ever been able to support life?" Michael Myer, the lead scientist of the Mars Exploration Program, summed up the mission ahead for Curiosity. NASA has been collecting evidence to inform that question since the first lander hit Mars in 1976.
"Over the last decade and a half of exploration, we have found more water than expected," Myers said, noting past discoveries of ice traces at the poles, subterranean glaciers and geologic imprints suggesting the presence of brine. The evidence indicates that Mars, at some point in the past, did have some of the resources to support life. NASA is landing Curiosity at a site where trace remnants of those resources are likely to be found.
The rover must find evidence of water, energy and carbon if scientists are to determine that life did exist on Mars at some point, said John Grotzinger, an MSL project scientist based at the California Institute of Technology.
"This is not something for which there is a slam-dunk discovery," Grotzinger said, "but many bits of information come together to build this, and it is going to take us a while to get there."
Gale Crater is located on a border between highlands and lowlands of the Martian surface. The crater is one of the lowest places identified in previous research, a likely spot for water to pool. Images returned from orbital craft show a geologic feature known as an "alluvial fan," indicating the onetime presence of a delta emptying into another body of water, and another good place to search for signs of an environment that might have supported life.
A mountain almost three kilometers in height rises from the middle of the crater, and it is another "exciting science target," Grotzinger said. Observations from space show that Mount Sharp, as the NASA team has named the mound, is made up of layers that will reveal different materials of clay and minerals, providing further insight to Mars history.
The MSL team used observations from previous missions to identify this particular site for study. Grotzinger said NASA engineers have made a "tremendous advance" to design the systems that will allow a precise landing in a predetermined location. System designs that promise greater accuracy and precision in flight all contribute to the body of knowledge that will allow astronauts to journey to Mars in the future.
The excitement is building at NASA for a complex planetary mission, and the agency is giving the public greater opportunities than ever before to see what scientists see as the rover sends back images of Mars. Using advances in video-gaming technologies, NASA will be offering downloads of a landing game that gives the player the controls to put the rover on the Martian surface. Other video, interactive and 3-D instructional materials will be available, in addition to open-house opportunities at NASA facilities involved in the MSL mission.
(This is a product of the Bureau of International Information Programs, U.S. Department of State.) 


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