That might help evolutionary biologists answer the question of why, for billions of years, and in every form of life on earth, only two base pairs are used.

ECONOMIST: A new kind of DNA

Earlier this month NASA unveiled its mission statement to revisit earth's satellite and create a permanent base there.

CNN: Mining the moon for a nuclear future

One could think of many reasons for considering a human base on Mars - such as over-population on Earth - but Darlene Lim is mainly motivated by the thrill of exploration.

BBC: Destination Mars on Earth

Eventually, ice deposits could provide water for a manned lunar base, which would otherwise have to bring its water expensively from earth.

ECONOMIST: Divining water

Russia says it also remains committed to sending cosmonauts beyond Earth's orbit in the future, including to a permanent base on the moon that it says could be used as a future launching pad for flights to Mars.

ENGADGET

The fall to Earth was monitored by the Joint Space Operations Center (JSPOC) at Vandenberg Air Force Base in California.

BBC: Nasa's UARS satellite falls off west coast of US