Posts Tagged ‘Extraterrestrial life

How Astronomers May Hunt for Life on Alien Planets

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This chart explains how astronomers measure the signatures of chemicals in the atmospheres of exoplanets.

Any sulfurous molecules that astronomers spot on alien worlds might be a way to reveal whether or not those distant planets host life, researchers suggest.
On Earth, microbes can live off the energy available in sulfurous molecules that volcanoes release, essentially “breathing” these compounds the way humans breathe oxygen. If a similar kind of metabolism evolved on an extrasolar planet, the sulfurous molecules detected in the atmosphere of that world might help reveal the presence of alien life, said researcher Renyu Hu, a doctoral student in planetary science at MIT.
To see what telltale signs any sulfur-dependent life might generate, Hu and his colleagues modeled Earth-sized planets in the habitable zones of sun-like stars — that is, areas where worlds could have liquid water on their surfaces. These simulated planets possessed nitrogen-based atmospheres like Earth but 1,000 times more sulfur.
Sulfur-dependent life on Earth releases hydrogen sulfide as waste. The researchers found these microbes could increase hydrogen sulfide levels by nearly 10 times what they would be on a planet without such life

A graphical representative of how the known alien solar systems stack up against our own Solar System.

From interstellar distances, it would be hard to distinguish hydrogen sulfide (H2S) from water (H2O) on the surfaces of exoplanets. However, the researchers calculate that extra atmospheric hydrogen sulfide would in turn cause more pure sulfur aerosols to form in the air, which astronomers could detect based on their distinctive spectra or fingerprint in the visible and infrared wavelengths.
“Hydrogen sulfide emissions from the surface would have a large impact on the atmospheric composition of a planet,” Hu said.
Still, no Earth-sized planets have been discovered yet in the habitable zones of sun-like stars. “Characterization of the atmospheres of exoplanets has been confined to close-in planets so far,” Hu said.
Also, Hu cautioned that hydrogen sulfide is not a conclusive signature of life. “We need to test our assumptions thoroughly,” he said. “It may be, for instance, that volcanism could produce tremendous amounts of that gas.”
Hydrogen sulfide is not the only biosignature gas the researchers are investigating.
“We want to study as many as possible — look at many, many gases in Earth’s atmosphere and see if they can be biosignatures as well,” Hu said.
Hu, with his colleagues Sara Seager and William Baines, detailed their findings May 26 at the American Astronomical Society meeting in Boston.
This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program.

Written by physicsgg

July 28, 2011 at 11:46 am

Ethane: A Fingerprint For Life On Exoplanets

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Before discussing the conclusions of this paper released this week, I’ll start with a pub-quiz style question. How much of Earth’s atmosphere has not been made by living things?
The answer is: less than 1%, which is mostly argon. The overwhelming majority is biogenic; the nitrogen is a product of denitrifying bacteria, the oxygen from plants, and the inconspicuous CO2 is produced by everything, but especially animals.
So, would an alien astronomer look at a spectrum of Earth, see this cocktail of gases, and think, “Hmmm. Clearly this planet is harbouring life?” The chances are that they would. Earth looks decidedly odd from a distance. It would show a combination of a water-rich atmosphere, combined with a strong ozone absorption; this ozone peak is basically a proxy for oxygen, and its presence implies a continuous biological source of oxygen – especially in combination with reduced species such as methane, nitrous oxide, and methyl chloride. Without being replenished, oxygen rapidly removes itself by reacting with other gases and things on the Earth (you should see my brother’s car!).

From Hanel et al 1975, Exploration of the Solar System by infrared imaging. Apologies for the poor quality photo of a textbook.

The problem is, oxygen can also be produced by non-biological processes, and moreover, life doesn’t necessarily produce oxygen anyway. In fact, life got on pretty much fine for a long period of time without oxygen before it was released en masse, in what you could call the greatest mass pollution event in Earth’s history. So long lived was this period that we might expect most alien life supporting planets to be harbouring single celled ETs…….Read more:

Written by physicsgg

June 17, 2011 at 8:30 am


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Did Phosphorus Power the Origin of Life?

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“Not only is phosphorus the active component of ATP, it also forms the backbone of DNA and is important in the structure of cell walls. But despite its importance to life, it is not fully understood how phosphorus first appeared in our atmosphere. One theory is that it was contained within the many meteorites that collided with the Earth billions of years ago.” Dr Terry Kee of the University of Leeds
(Image above is Mono Lake, site of the recent and controversial NASA discovery that ansenic may have replaced phosphorus position in microbial DNA).
Researchers at the University of Leeds may have uncovered new clues to the origins of life on Earth with the discovery of a compound known as pyrophosphite, which may have been an important energy source for primitive lifeforms.
There are several conflicting theories of how life on Earth emerged from inanimate matter billions of years ago — a process known as abiogenesis.
“It’s a chicken and egg question,” said Dr Terry Kee of the University of Leeds, who led the research. “Scientists are in disagreement over what came first — replication, or metabolism. But there is a third part to the equation, and that is energy.”
All living things require a continual supply of energy in order to function. This energy is carried around our bodies within certain molecules, one of the best known being ATP*, which converts heat from the sun into a useable form for animals and plants…. Read the rest of this entry »

Written by physicsgg

June 6, 2011 at 11:33 pm

Is there life on Mars? We may soon find out

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After 40 years of missions to Mars, its secrets could finally be within our reach
Forty years ago, space engineers launched a probe that would play a pivotal role in changing our understanding of our place in the cosmos. On 30 May 1971, Mariner 9 was dispatched to Mars on an Atlas Centaur rocket and in November that year slipped into orbit around the Red Planet.

In doing so, the American robot spaceship became the first manmade object to be placed in orbit around another planet. Humans had added an artificial satellite to another world. A few days later, two other spacecraft, Mars 2 and Mars 3, both built by the Soviet Union, followed suit and achieved Martian orbit. In three weeks, the Red Planet had become a scientific hotspot.

Thus began a revolution in our understanding of the solar system, a family of planets that space probes have shown to be far stranger and more exotic than expected, with Mars producing the largest number of surprises. Mariner 9 showed it possesses the solar system’s largest mountain and its biggest canyon, while ancient riverbeds and streams were discovered at several sites, findings that have been confirmed and explored in far greater detail by subsequent probes and which continue to maintain hopes that we will one day find signs of life on another world.

Forty years on, Mars is still a place of fascination for humanity, though its investigation has been a rocky business. “The story of Mars exploration has been a real rollercoaster,” admits Oxford astronomer Professor Fred Taylor, who has worked closely with Nasa on a number of missions to the planet. “Once, it seemed destined to support life. Then we thought it was utterly dead and featureless. Then we discovered – thanks to Mariner 9 – that it had a landscape through which water had poured. After that, craft found its soil contained no signs of biological material. Since then, we have bounced back and are hopeful life may exist deep underground.”….. Read the rest of this entry »

Written by physicsgg

June 5, 2011 at 12:34 pm


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Gold-mine worm shows animals could be living on Mars

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Is this what a Martian would look like? (Image: University Ghent, Belgium - Gaetan Borgonie)

“It’s like finding Moby Dick in Lake Ontario,” says Tullis Onstott of the nematode worms his Princeton University team discovered living far beneath the Earth’s surface in South Africa.
The tiny worms – just 500 micrometres long – were found at depths ranging from 900 metres to 3.6 kilometres, in three gold mines in the Witwatersrand basin near Johannesburg. That’s an astonishing find given that multicellular organisms are typically only found near the surface of the Earth’s crust – Onstott’s best guess is in the top 10 metres.
The creatures seem to live in water squeezed between the mines’ rocks, can tolerate temperatures reaching 43 °C and feed off bacteria. Carbon dating of the water they live in suggests that the worms have been living at these depths for between 3000 and 12,000 years.
“To have complex life sustain itself for such a long period completely sealed away from everything else – from sunlight, from surface chemistry – is pretty amazing,” says Caleb Scharf of the Columbia Astrobiology Center in New York City.

No place for a worm

Onstott says no one thought multicellular organisms would be found living in this so-called fracture water. He points out that microbiologists are still trying to prove and understand how even single-celled organisms can exist at these depths. “The lack of oxygen, temperature and food is a big dissuader,” he says.
“We’ve had this preconception that there can only be certain types of organisms in certain environments,” says Scharf. “But it’s not true at all. There are more complex organisms in these bizarre environments.”

Animals on Mars

If complex life forms are able to survive inside cracks deep inside Earth, it raises the possibility that they might have survived undetected in similar environments on Mars.
Carl Pilcher, director of NASA’s Astrobiology Institute in Moffett Field, California, points out that Onstott has previously discovered a bacterium living 2.8 kilometres underground, completely isolated from all other ecosystems on Earth (Science, DOI:10.1126/science.1127376). The bug gets its energy from the radioactive decay of elements in the surrounding rocks. “The significance was that you could imagine an ecosystem existing in the subsurface of a planet that didn’t have a photosynthetic biosphere, like Mars,” he says.
Until now, it was thought such an ecosystem could be made of bacteria only. But Onstott’s new findings have completely changed that. “It has extended the [earlier] work to an animal,” says Pilcher.
“These nematodes are grazing on microbes. So now you could imagine that if animal life had ever developed on a planet, and the surface of that planet became lifeless,” Pilcher explains, “you could imagine that animals [small enough to fit in tiny cracks] could coexist with microbial ecosystems all powered by radioactivity.”
Journal reference: Nature, DOI: 10.1038/nature09974

Written by physicsgg

June 2, 2011 at 7:32 pm

Posted in BIOLOGY

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