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Humans have scribbled "We were here" all over the solar system. From footprints on the moon to burnt-out landers on Titan, the visible records of our excursions past Earth are badges of pride — not to mention unique opportunities to do science.
"Aside from just a curiosity, it allows us to know exactly where all the lunar samples came from relative to one another," said planetary scientist Jeff Plescia of the Johns Hopkins University Applied Physics Lab, who uses the Lunar Reconnaissance Orbiter spacecraft to look for human artifacts on the moon.
But our tracks won't last forever. A new paper in the Journal of Geophysical Research traces how tracks left by the Mars rovers Spirit and Opportunity are wiped away by the wind, usually within a Martian year.
"It's a little humbling," said planetary scientist Paul Geissler of the U.S. Geological Survey, lead author of the new paper. "Mars will just clean up after us, and wait for the next visitors."
This gallery takes a quick tour through the solar system through the visible marks we've left behind.
Above:
Mars Rover Looks Back
One of the Mars exploration rovers looks back at where it's been. Image: NASA/JPL-Caltech/CornellSee Also:
- Where Will Next Mars Rover Land?
- Martian Dune Mystery Solved by Bouncing Sand Grains
- Inside the Soviets' Secret Failed Moon Program
- Lunar Probe Sends First High-Res Images
- The Moon Hides Ice Where the Sun Don't Shine
- First-Ever Photo of Liquid on Extraterrestrial World
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