‘With current technology, nothing larger or heavier than [the Mars Science Library, touching down on Mars in August 2012] can be put on the surface of Mars. Anything more massive, including a human mission, which NASA estimates would require landing at least 40 to 80 tons of machinery, is completely out of the question.

“We’ve maxed out our ability to take mass to the surface of Mars,” said engineer Bobby Braun, former NASA chief technologist and co-author of a 2005 research paper highlighting this problem.

The basic obstacle for large-scale missions is Mars’ tenuous atmosphere, which is more than 100 times thinner than that of Earth. The pressure of the Martian atmosphere at its surface is equivalent to what someone would experience flying at 100,000 feet on Earth.’ (via Wired.com). 

“For most researchers’ money, an Earth-like planet is the best bet for finding alien life. But looking in such an exclusive range of possibilities might give them only half the story.

A team of scientists is now proposing an index that ranks a planet’s habitability using a much wider set of criteria.

“We are trying not to be geocentric, calculating planetary habitability independent of liquid water,” said physicist Abel Mendez of the University of Puerto Rico in Arecibo and one of the co-authors of the new index, published in Astrobiology on Nov. 21.

Astronomers have discovered more than 700 extrasolar planets, many of them gas giants that orbit too near or far from their parent star to be comparable to Earth. But Mendez and his group want to expand the narrow possibilities generally considered necessary for a planet to host life.

The team proposes to rank planets on both an Earth Similarity Index (ESI) and also a broader Planetary Habitability Index (PHI). The first index looks at how close a planet is to Earth in mass, temperature, and composition while the second is based on the whether or not it possesses more exotic chemistries, liquids, and energy sources than found on our planet. Alien life could be based on elements other than carbon, require liquids other than water, and gain energy through means other than sunlight.” (via Wired.com).

Related:

• Through data, evaluating the potential for life on other worlds (89lp63.wordpress.com)
• Lighting ‘sprites’ in outer space may signal alien life (news.bioscholar.com)
• New system would assess odds of life on other worlds (nextbigfuture.com)
• System for assessing the odds of life on other worlds (scienceblog.com)
• Scientists rate livability of alien worlds (cosmiclog.msnbc.msn.com)