In 2005, NASA's Deep Impact probe shot an 800-pound subsidiary probe into the comet Tempel 1. Now, six years later, the new Stardust probe has returned to the comet to see our handiwork. But this isn't just about proving humanity can leave its mark anywhere in the cosmos - the artificially created crater kicked up valuable data about what's inside the comet's core.
Tempel 1 is about 3.7 miles wide and takes 5.5 years to complete its orbit around the Sun. Currently, the comet is located some 209 million miles, or 19 light-minutes, away from Earth. That's more than twice the distance between Earth and the Sun.
The 2005 Deep Impact mission was able to create an artificial crater about 500 feet across right between two larger, natural craters. Now that the poetically named Stardust probe has made it back to the comet, we can see how the crater churned up the inner core of the comet.
Brown University researcher Pete Schultz explains:
"We see a crater with a small mound in the center, and it appears that some of the ejecta went up and came right back down. This tells us this cometary nucleus is fragile and weak based on how subdued the crater is we see today."
Indeed, the crater appears to be in the process of repairing itself, as the ejected materials kicked up by the explosion have resettled and started to fill back in the hole. Even more dramatic was what was going on around the Stardust probe - it had to fly through a thick cloud of large comet particles to get the photos, and some of the objects penetrated through multiple layers of the craft's shielding.
Stardust scientist Don Brownlee explains what the probe was going through:
"The data indicate Stardust went through something similar to a B-17 bomber flying through flak in World War II. Instead of having a little stream of uniform particles coming out, they apparently came out in chunks and crumbled."
Despite taking a pounding, Stardust completed its mission and has given NASA scientists a ton of vital new data to work with. Says project leader Joe Veverka:
"This mission is 100 percent successful. We saw a lot of new things that we didn't expect, and we'll be working hard to figure out what Tempel 1 is trying to tell us."