Space Junk an Orbital Hazard; On Mars, Rover Finds New Rock
By Charlene Porter
Washington - Debris circling the Earth in a low orbit is becoming a serious hazard, a danger to spacecraft and astronauts, and NASA needs a plan to reduce the hazard, an expert advisory panel reported September 1.
The U.S. space agency is keeping track of about 22,000 pieces of this debris, known as space junk. But the report from the National Research Council (NRC) released September 1 estimates another 500,000 bits of stuff, 10 centimeters or less, are out there. And bits of debris less than 1 centimeter? The NRC estimates tens of millions of those.
Derelict satellites, equipment lost from missions, paint fragments, space wreckage and meteoroids form the orbital clutter that only can get worse.
"Existing objects are more likely to collide with other debris and produce additional smaller pieces, increasing the chance of further collisions and satellite failure," according to the report, "Limiting Future Collision Risk to Spacecraft."
NASA has been trying to keep an eye on space junk since 1979, but the small bits can't be tracked with current technologies. Meteoroids are tiny particles of comets or asteroids that travel through space and veer into Earth's atmosphere. Once again, today's science can't follow their paths toward our planet.
NASA has adopted some protective equipment for its spacecraft, notably a form of shielding added to the International Space Station, but the problem is growing beyond the effectiveness of passive technologies and the expense they add to missions.
Sending a cleaning crew into space might sound like a solution, but the report points out complexities of international law that inhibit such an effort. Seventy percent of the cataloged pieces of space junk came from non-U.S. space missions, and international legal precedents prohibit one nation from salvaging or collecting objects that belong to another government.
While it outlines the problem in detail, the NRC report offers no ready solutions. It recommends that NASA collaborate with commercial, national and international agencies to devise solutions for debris avoidance, mitigation and surveillance.
ROVER'S NEW TERRITORY
The space rover Opportunity left Earth behind long ago. It has spent more than seven years observing, sampling and roaming the surface of Mars. Scientists at the Jet Propulsion Laboratory (JPL) who study the data the craft sends back announced September 1 that the newest patch of Martian ground Opportunity is exploring yields rocks unlike anything studied before. The rover arrived several weeks ago on the rim of a large crater that the scientists named Endeavour.
"This is different from any rock ever seen on Mars," said Steve Squyres, principal investigator for Opportunity at Cornell University. It's almost as if the arrival at Endeavour has "given us the equivalent of a second landing site for Opportunity," Squyres said in a NASA briefing.
The Opportunity team has reason to believe that some rock exposures on Endeavour's rim may date from early in Martian history and include clay minerals that could be more favorable to life. They are guiding the rover to a rock ridge that "looks like sedimentary rock that's been cut and filled with veins of material possibly delivered by water," said Ray Arvidson, an investigator on the mission from Washington University in St. Louis.
Opportunity has been working what NASA calls "bonus overtime" since 2004 when the craft completed the 90-day mission for which it was designed - to study the history of environmental conditions at sites where trace evidence suggested the presence of water at some point in the past. Opportunity, and its twin craft Spirit, both found geologic indicators of a watery past at the two very different sites where they landed.
After those first three months, scientists directed the vehicles to other locations on the Martian surface, continuing the search for evidence of water. Spirit continued to send back useful data until 2010, when communications were lost. So far, Opportunity has driven more than 30 kilometers, 50 times the distance originally planned for the mission.
With a career far longer than ever anticipated, Opportunity could experience a system failure at any moment. In the meantime, the JPL team is happy to study whatever new visions of Mars the craft returns.
A next-generation Mars rover is soon to begin its voyage, with a launch window starting in late November and lasting about three weeks.
(This is a product of the Bureau of International Information Programs, U.S. Department of State.)