Ancient Mars lake could have supported life, Curiosity rover shows

NASA's Curiosity rover has found evidence of an ancient Martian lake that could have supported life as we know it for long stretches — perhaps millions of years.

This long and skinny freshwater lake likely existed about 3.7 billion years ago, researchers said, suggesting that habitable environments were present on Mars more recently than previously thought.

"Quite honestly, it just looks very Earth-like," said Curiosity lead scientist John Grotzinger, of the California Institute of Technology in Pasadena. [Ancient Mars Could Have Supported Life (Photos)]

"You've got an alluvial fan, which is being fed by streams that originate in mountains, that accumulates a body of water," Grotzinger told SPACE.com. "That probably was not unlike what happened during the last glacial maximum in the Western U.S."

Habitable Mars
The lake once covered a small portion of the 96-mile-wide Gale Crater, which the 1-ton Curiosity rover has been exploring since touching down on the Red Planet in August 2012.

'Quite honestly, it just looks very Earth-like.'

- Curiosity lead scientist John Grotzinger, of the California Institute of Technology in Pasadena

The main task of Curiosity's $2.5 billion mission is to determine whether Gale Crater could ever have supported microbial life. The rover team achieved that goal months ago, announcing in March that a spot near Curiosity's landing site called Yellowknife Bay was indeed habitable billions of years ago.

The new results, which are reported Monday, Dec. 9, in six separate papers in the journal Science, confirm and extend Curiosity's landmark discovery, painting a more complete picture of the Yellowknife Bay area long ago.

This picture emerged from Curiosity's analysis of fine-grained sedimentary rocks called mudstones, which generally form in calm, still water. The rover obtained powdered samples of these rocks by drilling into Yellowknife Bay outcrops.

The mudstones contain clay minerals that formed in the sediments of an ancient freshwater lake, researchers said. Curiosity also spotted some of the key chemical ingredients for life in the samples, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.

The lake could have potentially supported a class of microbes called chemolithoautotrophs, which obtain energy by breaking down rocks and minerals. Here on Earth, chemolithoautotrophs are commonly found in habitats beyond the reach of sunlight, such as caves and hydrothermal vents on the ocean floor.

"It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake's calm waters, converting a rich array of elements into energy," Sanjeev Gupta of Imperial College London, co-author of one of the new papers, said in a statement.

An icy Martian lake?
The shallow ancient lake may have been about 30 miles long by 3 miles wide, Grotzinger said. Based on the thickness of the sedimentary deposits, the research team estimates that the lake existed for at least tens of thousands of years — and perhaps much longer, albeit on a possibly on-and-off basis.

Taking into account the broader geological context, "you could wind up with an assemblage of rocks that represent streams, lakes and ancient groundwater systems — so for times when the lake might have been dry, the groundwater's still there. This could have gone on for millions or tens of millions of years," Grotzinger said.

The lack of weathering on Gale Crater's rim suggests that the area was cold when the lake existed, he added, raising the possibility that a layer of ice covered the lake on a permanent or occasional basis. But such conditions wouldn't be much of a deterrent to hardy microbes.

"These are entirely viable habitable environments for chemolithoautotrophs," Grotzinger said.

Researchers still don't know if the Gale Crater lake hosted organisms of any kind; Curiosity was not designed to hunt for signs of life on Mars. But if chemolithoautotrophs did indeed dominate the lake, it would put an alien twist on a superficially familiar environment.

"You can imagine that, if life evolved on Mars and never got beyond the point of chemolithoautotrophy, then in the absence of competition from other types of microbes, these systems might have been dominated by that type of metabolic pathway," Grotzinger said. "And that's an un-Earth-like situation."

Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

View the original article here

Exploded Star's Guts Shining Bright Again, Photo Shows (SPACE.com)

The glowing entrails of an exploding star, thought to have faded over time, now appear to be lighting up again, a new Hubble Space Telescope photo reveals.

NASA released the new Hubble image of the well-known star explosion, called Supernova 1987A, today (June 10). The photo shows the closest supernova explosion witnessed in almost 400 years. This has allowed astronomers to study it in unprecedented detail as the outburst evolves.

In the latest study of Supernova 1987A a team of astronomers announced that the debris from the explosion that had faded over the years is brightening. This suggests that the star explosion, which is located 165,000 light-years away in the Large Magellanic Cloud (a close neighbor of our own Milky Way galaxy),  is turning into a so-called supernova remnant. [See Hubble's new photo of Supernova 1987A]

The research is detailed in the June 9 edition of the journal Nature.

Supernovas typically transition into remnants when the exploded material starts to fade, but the brightness increases due to interactions between the debris cloud and surrounding gas. This cosmic shift is usually difficult for astronomers to study, but due to the relatively close proximity of the Large Magellanic Cloud, astronomers have been able to make detailed observations of Supernova 1987A periodically from 1994 to 2009.

"Supernova 1987A has become the youngest supernova remnant visible to us," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "It's only possible to see this brightening because SN 1987A is so close and Hubble has such sharp vision."

Kirshner leads a long-term study of SN 1987A using the Hubble Space Telescope. Since its launch in 1990, Hubble has provided a continuous record of the changes in the supernova.

In the new Hubble image, SN 1987A is surrounded by a ring of material that blew off the star thousands of years before it exploded. The ring extends about one light-year (about 6 trillion miles or 9.5 trillion km) across. Inside that ring, the star's guts are rushing outward in an expanding debris cloud.

Most of the light from the supernova comes from radioactive decay of elements that were created in the explosion. This light fades over time, but the brightening of SN 1987A's debris suggests that a new power source is lighting it.

The debris of 1987A is beginning to impact the surrounding ring, which is creating powerful shock waves that produce X-rays that can be observed by NASA's Chandra X-ray Observatory. Those X-rays are illuminating the supernova debris and the heated shock waves are making it glow. This same process powers well-known supernova remnants in our own galaxy, like Cassiopeia A.

Furthermore, since SN 1987A is still young, astronomers can study the remnants of the explosion to decode its history.

Eventually, that history will be lost when the bulk of the expanding stellar debris impacts the surrounding ring and shreds it, researchers said. But, until then, SN 1987A offers astronomers the opportunity to watch as a supernova changes, they added.

Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

View the original article here