Ammonia on Mars could mean life

by Dr David Whitehouse, BBC

Reposted from:
http://news.bbc.co.uk/2/hi/science/nature/3896335.stm

Ammonia may have been found in Mars' atmosphere which some scientists say could indicate life on the Red Planet.

Researchers say its spectral signature has been tentatively detected by sensors on board the European Space Agency's orbiting Mars Express craft.

Ammonia survives for only a short time in the Martian atmosphere so if it really does exist it must be getting constantly replenished.

There are two possible sources: either active volcanoes, none of which have been found yet on Mars, or microbes.

Suite of molecules

"Ammonia could be the key to finding life on Mars," one US space agency (Nasa) scientist told BBC News Online.

Spectral evidence for the gas was seen by the Planetary Fourier Spectrometer (PFS) on Mars Express.

Professor Vittorio Formisano, principal investigator for the instrument, is expected to release details of new findings from the PFS at an international conference being held next week in Paris.

The PFS is sensitive to radiation in the spectral region of 1.2-5 microns and 5-50 microns - a region rich with important molecules such as water and carbon dioxide. Ammonia has a spectral line at 10 microns.

Although Mars Express has been in orbit around Mars since December 2003, scientists have so far only analysed a fraction of the data the PFS has produced.

Researchers say this is because they are still coming to terms with the complexities of the PFS as well as coping with some nagging power problems on Mars Express.

So far the PFS has observed a depletion of carbon dioxide and an enrichment of water vapour over some of the large extinct volcanoes on Mars.

But it is the detection of minor compounds, possible in the sensors high-resolution mode, which are causing excitement.

The tentative detection of ammonia comes just a few months after methane was found in the Martian atmosphere. Methane is another gas with a possible biological origin.

Ammonia is not a stable molecule in the Martian atmosphere. If it was not replenished in some way, it would only last a few hours before it vanished.

One possibility the scientists have had to rule out is that the ammonia comes from the air bags of the failed Beagle 2 mission. Analysis has revealed that the suspected ammonia's distribution is not consistent with this explanation.

Life on Mars?

The importance of ammonia is that it is a compound of nitrogen and hydrogen.

Nitrogen is rare in the Martian environment but because no form of terrestrial life can exist without it, the presence of ammonia may indicate that Martian microbial life is hoarding it.

"There are no known ways for ammonia to be present in the Martian atmosphere that do not involve life," the Nasa scientist said.

The twin US rovers that landed on the Red Planet in January will be unable to answer the question of the ammonia's origin as they are designed for geological work.

But future missions could include sensors to analyse the ammonia to determine if it has a biological or volcanic origin. Lava deposited on to the surface, or released underground, could produce the gas.

But, so far, no active volcanic hotspots have been detected on the planet by the many spacecraft currently in orbit.

Methane found on distant world

Methane found on distant world

By Helen Briggs Science reporter, BBC News

The planet is a "hot Jupiter" blasted by starlight

A carbon-containing molecule has been detected for the first time on a planet outside our Solar System.

The organic compound methane was found in the atmosphere of a planet orbiting a star some 63 light years away.

Water has also been found in its atmosphere, but scientists say the planet is far too hot to support life.

The discovery, unveiled in the journal Nature, is an important step towards exploring new worlds that might be more hospitable to life, they say.

Methane, made up of carbon and hydrogen, is the simplest possible organic compound.

HD 189733b Located 63 light years from Earth, in the constellation Vulpecula, the little fox About the size of Jupiter but orbits closer to the parent star in its Solar System than Mercury does in our own Temperatures reach 900 degrees C, about the melting point of silver

Under certain circumstances, methane can play a key role in prebiotic chemistry - the chemical reactions considered necessary to form life.

Scientists detected the gas in the atmosphere of a Jupiter-sized planet known as HD 189733b.

Co-author Giovanna Tinetti from University College, London, told BBC News: "This planet is a gas giant very similar to our own Jupiter, but orbiting very close to its star.

"The methane here, although we can call it an organic constituent, is not produced by life - it is way too hot there for life."

Stepping stone

Dr Tinetti, and co-authors Mark Swain and Gautam Vasisht, from Nasa's Jet Propulsion Laboratory in Pasadena, California, found the tell-tale signature of methane in the planet's atmosphere using the Hubble Space Telescope.

The observations were made as the planet passed in front of its parent star, as viewed from Earth. As the star's light passed briefly through the planet's atmosphere, the gases imprinted their chemical signatures on the transmitted light.

My personal view is it is way too arrogant to think that we are the only ones living in the Universe Dr Giovanna Tinetti

A method known as spectroscopy, which splits light into its components, revealed the chemical "fingerprint" of methane.

The researchers also confirmed a previous discovery - made by Nasa's Spitzer Space Telescope - that the atmosphere of HD 189733b also contains water vapour.

It shows that Hubble, Spitzer and a new generation of space telescopes yet to be launched can detect organic molecules on other extrasolar planets using spectroscopy, they say.

Dr Swain said: "This is a crucial stepping stone to eventually characterising prebiotic molecules on planets where life could exist."

Dr Tinetti said the technique could eventually be applied to extrasolar planets that appear more suitable for life than HD 189733b.

She said:

"I definitely think that life is out there. My personal view is it is way too arrogant to think that we are the only ones living in the Universe."

Real worlds

The number of known planets orbiting stars other than our own now stands at about 270.

For most of them, scientists know little more than the planet's mass and orbital properties.

Adam Showman of the Department of Planetary Sciences at the University of Arizona, US, said scientists were finally starting to move beyond simply discovering extrasolar planets to truly characterising them as worlds.

Dr Showman, who was not part of the study, said:

"The discovery does not by itself have any direct implications for life except that it proves a technique which might potentially be useful for characterising the atmosphere of rocky planets when we finally start discovering them."

Excitement about finding other Earth-like planets is driven by the idea that some might contain life; or that perhaps, centuries from now, humans might be able to set up colonies on them.

The key to this search is the so-called "Goldilocks zone", an area of space in which a planet is "just the right distance" from its parent star so that its surface is not-too-hot or not-too-cold to support liquid water.