关于这张图
This is a Hygrochron sensor. Sensors were buried at different depths, to see how the temperature and moisture levels in the ground changed close to and farther from the surface. Special permission from the National Park Service is needed to dig at Racetrack Playa. Photo credit: NASA/GSFC/Maggie McAdam To read a feature story on the Racetrack Playa go to: <a href="http://www.nasa.gov/topics/earth/features/roving-rocks.html" rel="nofollow">www.nasa.gov/topics/earth/features/roving-rocks.html</a> <b><a href="http://www.nasa.gov/centers/goddard/home/index.html" rel="nofollow">NASA Goddard Space…
