Top 10 Scientific Discoveries of 2013

Mars and Microbes
Curiosity has had a busy couple of months on Mars drilling into rocks and discovering some of the key building blocks for life. Image courtesy NASA/JPL-Caltech/MSSS

Seven months after a NASA rover landed on Mars, scientists announced in March that the rover, Curiosity, found evidence the red planet could have been home to living microbes.

Here's how that happened: On Feb. 8, Curiosity drilled into a rock and found some of the key ingredients for life, including sulfur, nitrogen and oxygen. The rock was sitting in a part of Mars called Yellowknife Bay, which scientists say, was at the end of an ancient river system or lake bed. The rock contained minerals usually found in clay [sources: Wall, NASA].