NASA's Mars Curiosity rover has found methane in the Martian atmosphere and organic chemicals in the planet's soil, the latest hint that Mars was once suitable for microbial life.
The rover also found organic chemicals in a soil sample collected by a robotic drill. They were the latest findings as NASA hunts for clues about the possibility of extraterrestrial life.
Last week, scientists determined that billions of years ago, a lake filled the 96-mile-wide crater being explored by Curiosity.
The finding was another hint that Mars, the planet most like Earth in the solar system, was once suitable for microbial life.
The rover has travelled around five miles since landing on Mars in August of 2012.
It has been exploring an area where rocks have been found containing water-deposited sediments to learn if the life-friendly environments actually existed long enough for life to evolve.