516986main_n30037te01.jpg

If any intelligent life existed on comet Tempel-1, it might wonder why humans had become so interested in it, among the thousands of comets that orbit the sun. Back in 2005, the Deep Impact spacecraft flew by the craft and fired what Time called a "copper cannonball" onto its surface to create a plume of rock and ice that could be analyzed.

Repurposing the the Stardust spacecraft, which successfully carried out its main mission in 2006, NASA scientists got a second chance at analyzing Tempel-1 earlier this week. Very late on Valentine's Day, they flew by the craft and snapped pictures of it. Astronomers want to see how much Tempel's 5.5-year orbit around the sun has changed the little 3.7-mile wide object. That could provide them with important evidence about how comets evolve as they travel from very close to the sun out to the outer reaches of the solar system.

View more Pictures of the Day.

Image: NASA.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.