Comet Hartley 2

NASA's robotic space probe EPOXI/Deep Impact approached Comet Hartley-2 on November 4, 2010, for the fifth – and closest – time. The probe, which came within approximately 700 kilometers (435 miles), returned the first ever photographs of the comet’s nucleus. 

These images were taken around the approximate time of closest approach. Although this image is unprocessed, some surface features of the comet’s icy nucleus are visible. For instance, jets appear to be ejecting vapor into space along the comet’s bottom right-hand surface. (Further analysis will have to wait until higher resolution, processed photographs become available.)

Understanding Auroras

In 2007, NASA launched THEMIS (Time History of Events and Macroscale Interactions during Substorms), a 2-year mission to improve the understanding of how severe space weather effects on Earth. 

The mission consisted of five identical probes that orbit the earth and line up over the United States every four days. In this artist's rendering, THEMIS' main orbits are represented by red ovals. Blue lines represent the Earth's magnetic field. The white flash represents energy released during substorms.