Cape Canaveral, Florida: Nasa is headed back to Mars, this time with a robotic scout named Maven that will attempt to solve the mystery of the red planet's radical climate change.
Maven is scheduled to blast off aboard an unmanned rocket at 1.28pm EST (1828 GMT) on Monday.
The journey to Mars will take 10 months, putting Maven in orbit around the red planet in September 2014.
The spacecraft will circle the red planet for a full Earth year, examining the upper atmosphere.
It will dip as low as 78 miles (125 kilometres) above Mars to sample the atmosphere. Its orbit will extend as high as 3,864 miles (6,218 kilometres).
Scientists want to learn how Mars transformed from a warm, wet planet a few billion years ago to the dry, cold world of today.
The atmosphere went from thick to thin. Much of the atmospheric gas may have escaped into space. The sun is the likely culprit.
