* Astronomy

We've been trying to make contact with aliens for years. Now the day is fast approaching when we might finally succeed. But will our extraterrestrial friends come in peace? Or will they want to eat us? Astronomer David Whitehouse explores the perils of a close encounter
We are making dangerous discoveries in space. In April, astronomers found, on our cosmic doorstep, a planet dubbed Gliese 581c. Nestling close to a dim red star, it's a rocky world only a little larger than Earth. Like Earth, it could support liquid water. And to scientists, liquid water means the possibility of life.

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Historically, crossing oceans and setting up farmsteads on new lands conveniently stripped of indigenous inhabitants by disease has been a cost-effective proposition. But the scale factor involved in space travel is strongly counter-intuitive.
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With the help of a $6.5 million grant from NASA, Wisconsin  researchers will join the hunt for extraterrestrial life and early life  on Earth by developing techniques and instruments to read the chemical signatures living organisms leave in rocks and minerals.
With the new award, University of Wisconsin-Madison scientists and their collaborators from the University of Georgia and the Jet Propulsion Laboratory (JPL) will become a key part of NASA's Astrobiology Institute.

"The long-term goal is to understand when life began on Earth, what are the criteria for determining that life existed on another planetary body. What we're looking for is the signature of  past life as preserved in minerals"- Clark Johnson, the UW-Madison professor of geology and geophysics leading the new effort.

If life existed elsewhere in our solar system or beyond, odds are it  would have been single-celled organisms such as bacteria, which can leave  a chemical trail preserved in stone. Such is the case with microbes on  Earth. Scientists have developed a bevy of techniques to read those  chemical signatures to understand something about life that existed on  Earth hundreds of millions or even billions of years ago. Earth, in fact, will be the laboratory for the new initiative as  researchers seek to refine their understanding of the chemical impressions  left by ancient bacteria and other microorganisms. Such a baseline will  give scientists an interpretive framework for analysing samples from  Mars and other places beyond our planet that may have once harboured life.
 Such context was lacking with the Allan Hills meteorite, a suspected  piece of Mars found in Antarctica and theorized to be one of the oldest  relics of our solar system at 4.5 billion years old. The meteorite made  news in 1996 with the publication of a paper suggesting that tiny  features in the rock might be artefacts of ancient Martian life.
That evidence, it turns out, is now discounted by most scientists.  Thus, any future sample purported to harbour evidence of extraterrestrial  life will be the subject of intense scientific scrutiny.

"The bar is  really high. The (scientific) community is not going to  believe it unless the interpretive framework behind it is fully  developed"- Clark Johnson.

To help achieve that, Johnson's group plans an isotopic approach as a  way to ferret out the signatures of life from rocks that may be hundreds  of millions or billions of years old. Most elements have different  masses called isotopes, and very subtle changes can occur during biological  reactions.

"Geologists are good at going back in time, and we will explore the  isotopes in very ancient rocks"- Clark Johnson.

The allure of chemical isotopes as biosignatures, Johnson says, resides  not only in their ability to identify the chemical fossils of past  life, but also in their great durability.
Any sample will have a complicated history and may  have endured many changes over long periods of time. For example, minerals  from another planet may have been exposed to large doses of ultraviolet  radiation for billions of years, or geologic processes that can  potentially change their composition. But the isotopic makeup of elements that  were cycled by living creatures, Johnson notes, tend to resist such  change.
His group will first compile an inventory of organic materials such as  carbon, and in simulated planetary environments, test their  survivability to assemble a plausible inventory of things to look for on another  planet.

"We'll look for terrestrial analogues that we can really pull apart"- Clark Johnson.

In recent years, scientists have found numerous Earthbound microbes  that live in extremely hot and chemically forbidding environments, and it  has been long known that microbial life can live off of and process  elements such as iron. Knowing the kinds of signatures they leave behind  will be a big help when samples from other planets become the subject of  scientific scrutiny.
The new project, Johnson hopes, will exert influence on future NASA  missions. Ultimately, his group will help with the development of a  miniature mass spectrometer and other instruments that could be deployed by a  probe to search for signs of past life on Mars or other planets.

Source University of Wisconsin-Madison

Derelict rocket stages that propelled four spacecraft toward the edges of our solar system and beyond are likely carrying Earthly bacteria out into the galaxy.
The four 'STAR' upper rocket stages, also known as kick motors, are responsible for booting Voyager 1, Voyager 2 and Pioneer 10 to the solar system's fringes, as well as sending NASA's New Horizons spacecraft on a path to Pluto. The rocket stages are themselves on course to move beyond the sun's influence into interstellar space.

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