Did lack of comet impacts help life evolve?

• 28 November 2008 by David Shiga
• Magazine issue 2684.

IT SEEMS we got off lightly in the cosmic lottery. Deadly comet impacts may be much rarer in our solar system than in others nearby.

We can't directly measure the rate of comet collisions in other solar systems but we can detect signs of the dust that such smashes kick up because the dust gets warmed by the star and so gives off infrared radiation. That radiation shows up as extra infrared in the spectrum of light coming from the star. Because such dust should dissipate quickly, it is thought to provide a good snapshot of the recent collision rate.

Jane Greaves of the University of St Andrews, UK, analysed observations by the Spitzer Space Telescope and found that

the vast majority of sun-like stars near us have more dust than our solar system does and therefore have had more collisions in their vicinity. Our solar system may be one of the few that have been safe for life.

Greaves presented her results at the Cosmic Cataclysms and Life symposium in Frascati, Italy, this month.

more...

Exoplanets finally come into view

source: BBC

Three exoplanets orbiting the same star have been imaged directly

The first pictures of planets outside our Solar System have been taken, two groups report in the journal Science.

Visible and infrared images have been snapped of a planet orbiting a star 25 light-years away.

The planet is believed to be the coolest, lowest-mass object ever seen outside our own solar neighbourhood.

In a separate study, an exoplanetary system, comprising three planets, has been directly imaged, circling a star in the constellation Pegasus.

While several claims have been made to such direct detection before, they have later been proven wrong or await confirmation.

It's a profound and overwhelming experience to lay eyes on a planet never before seen Paul Kalas, University of California

The search for exoplanets has up to now depended on detecting either the wobble they induce in their parent star or, if their orbits are side-on to telescopes, watching them dim the star's light as they pass in front of it.

Being able to directly detect the light from these planets will allow astronomers to study their composition and atmospheres in detail.

Ring cleaning

The difficulty for astronomers imaging exoplanets is that their parent star's light swamps them - like trying to spot a match next to a floodlight at a distance of a mile.

The light from the star Fomalhaut was blocked to spot the planet Enlarge Image

But advances in optics and image processing have allowed astronomers to effectively subtract the bright light from stars, leaving behind light from the planets. That light can either come in the infrared, caused by the planets' heat, or be reflected starlight.

Paul Kalas of the University of California, Berkeley, led an international group that used the Hubble Space Telescope to image the region around a star called Fomalhaut in the constellation Piscis Austrinus.

The star has a massive ring of dust surrounding it that appears to have a cleanly groomed inner edge.

That is in keeping with what is known as accretion theory - that young planets gather up dust and matter as they orbit - and prompted the team to begin looking for the suspected planet in 2005.

The team estimates that the planet, designated Fomalhaut b, is some 18 billion kilometres (11 billion miles) away from its star, about as massive as Jupiter and completes an orbit in about 870 years. It may also have a ring around it.

"I nearly had a heart attack at the end of May when I confirmed that Fomalhaut b orbits its parent star," Dr Kalas said. "It's a profound and overwhelming experience to lay eyes on a planet never before seen."

An artist's concept of the star Fomalhaut and the planet observed by Hubble

Christian Marois of the Herzberg Institute for Astrophysics, Canada, and his team used the Keck and Gemini telescopes in Hawaii to look near a star called HR 8799, which is just visible to the naked eye.

The team studied light in the infrared part of the spectrum, hoping to spot planets that were still hot from their formation.

What they found in 2004, and confirmed again this year, are three planets circling the star.

According to a theoretical model that accounts for the light coming from the planets, they range in size from five to 13 times the mass of Jupiter and are probably only about 60 million years old.

The trio have similarities with our own Solar System. Their orbits are comparable in size to those of the outer planets, and the smaller planets are those closest to the Sun - again suggesting a system that formed through accretion.

Dr Marois points out that the current methods used in the exoplanet hunt are sensitive primarily to Jupiter-sized planets and larger.

"We thus do not have a full picture," he told BBC News. "The detection of the three planets around HR 8799 does not mean that no planets are orbiting at smaller separations. Other gas giant or even rocky planets could reside there."

A to-scale comparison of the HR 8799 system and our own

The study of the light directly from the planets will yield information about their atmospheres and surfaces that is impossible to collect from planets discovered indirectly.

Further, the current results will also support theories of how planets form from the grand discs of dust and material around stars, and lead to better estimates of how many Earth-like planets are likely to exist.

These latest claims are both based on observations that were well-spaced in time, allowing the researchers to apply a rigorous test for direct detection.

"You see an object next to a star and you might think it's a planet," commented Mark McCaughrean, an astrophysicist at the University of Exeter, UK.

"But you have to watch it for several years and make sure that it moves around the star and with the star as it moves across the sky. Though I've been very sceptical in the past, these ones all seem pretty real to me," he told BBC News

"It's like a London bus - you've been waiting for one for ages and suddenly four come along at once.

Cassini might hold secrets to life on Saturn moon

Cassini might hold secrets to life on Saturn moon

• 18:17 03 November 2008
• NewScientist.com news service
• Rachel Courtland

Enlarge image

Jets of fine, icy particles erupt from the south polar region of Enceladus (Image: NASA/JPL/Space Science Institute)

Habitable worlds may hide in gas giants' wake

Habitable worlds may hide in gas giants' wake

• 01 November 2008

HABITABLE planets may be lurking in the wake of Jupiter-like planets as they orbit distant stars.

When a gas giant coalesces from the swirling nebula of gas and dust surrounding a young star, the planet's gravity forms a wake ahead and behind it, concentrating enough matter there for it to clump together and form smaller, rocky planets like Earth. That's according to simulations led by Wladimir Lyra of the Uppsala Astronomical Observatory in Sweden. Objects born in Jupiter's wake may have merged to form the planet Saturn, which was then nudged into its current position by the gravity of other planets, the team says (www.arxiv.org/abs/0810.3192).

Outside our solar system, some gas giant planets have been detected in the habitable zone of their stars. Their wakes may harbour rocky, Earth-size worlds. "It's an exciting possibility," says Sara Seager of MIT. She notes that such planets could be found by the small gravitational tugs they exert on their larger, known siblings, an idea supported by recent calculations by Nikku Madhusudhan and Joshua Winn, also of MIT.

Goldmine bug DNA may be key to alien life

• 19:00 09 October 2008
• NewScientist.com news service
• Catherine Brahic

See our online special report The most extreme lifeforms in the universe

A bug discovered deep in a goldmine and nicknamed "the bold traveller" has got astrobiologists buzzing with excitement. Its unique ability to live in complete isolation of any other living species suggests it could be the key to life on other planets.

A community of the bacteria Candidatus Desulforudis audaxviator has been discovered 2.8 kilometres beneath the surface of the Earth in fluid-filled cracks of the Mponeng goldmine in South Africa. Its 60°C home is completely isolated from the rest of the world, and devoid of light and oxygen.

Dylan Chivian of the Lawrence Berkeley National Laboratory, California, studied the genes found in samples of the fluid to identify the organisms living within it, expecting to find a mix of species. Instead, he found that 99.9% of the DNA belonged to one bacterium, a new species. The remaining DNA was contamination from the mine and the laboratory.

"The fact that the community contains only one species stands one of the basic tenets of microbial ecology on its head,"

says Carl Pilcher, director of the NASA Astrobiology Institute, who was not involved in Chivian's DNA analysis but whose team made the initial discovery that there were microbes living in this particular fissure two years ago.

Evolutionary biologist E. O. Wilson says the discovery is so important he will at once begin to mention it in his lectures on biodiversity.

Lonely bug

A community of a single species is almost unheard of in the microbial world. It means the ecosystem's only species must extract everything it needs from an otherwise dead environment.

"Virtually all other known ecosystems on Earth that don't use sunlight directly do use some product of photosynthesis," says Pilcher.

Deep-sea vent communities, for instance, are too far down to directly use sunlight but they do use oxygen dissolved in seawater, and that oxygen is produced by photosynthesising plankton at the surface.

Chivian's analysis shows that D. audaxviator gets its energy from the radioactive decay of uranium in the surrounding rocks. It has genes to extract carbon from dissolved carbon dioxide and other genes to fix nitrogen, which comes from the surrounding rocks. Both carbon and nitrogen are essential building blocks for life as we know it, and are used in the building blocks of proteins, amino acids. D. audaxviator has genes to produce all the amino acids it needs.

D. audaxviator can also protect itself from environmental hazards by forming endospores – tough shells that protect its DNA and RNA from drying out, toxic chemicals and from starvation. It has a flagellum to help it navigate.

Ancient origins?

"One question that has arisen when considering the capacity of other planets to support life is whether organisms can exist independently, without access even to the Sun," says Chivian. "The answer is yes and here's the proof. It's philosophically exciting to know that everything necessary for life can be packed into a single genome."

Chris McKay, of NASA's Ames Research Center says that

D. audaxviator is an amazing discovery, and represents the kind or organism that could survive below the surface of Mars or Saturn's sixth largest moon Enceladus.

Some of the bacterium's genes appear to be inherited from a related species. Others have been found in archaea, a group of organisms evolutionarily distinct from bacteria. Chivian says D. audaxviator may have evolved as it travelled down through the cracks in the rock, and acquired archaea genes through horizontal gene transfer from populations it crossed on its way down.

"It can't handle oxygen," he says. This suggests it has not been exposed to pure oxygen for a long time. The water in which D. audaxviator lives has not seen the light of day in over 3 million years, and this could be an indication of how old the species is.

In fact, the species got its name from its long journey towards the centre of the Earth. In Jules Verne's novel by that name, the fictional Professor Lindenbrock's journey is triggered by the following message in Latin: "descende, Audax viator, et terrestre centrum attinges" – meaning "descend, bold traveller, and attain the center of the Earth".

Journal reference: Science (DOI: 10.1126/science.1155495)

See our online special report The most extreme lifeforms in the universe

Astrobiology – Learn more in our out-of-this-world special report.

Is Our Solar System a Rarity in Milky Way? Scientists Say "Yes"

There goes the escape route for Dick'n'George.

clipped from www.dailygalaxy.com Three Northwestern University researchers have learned that our solar system in which the Earth orbits our sun is the exception in the Milky Way rather than the rule. "We now know that these other planetary systems don't look like the solar system at all," said Frederic A. Rasio, senior author of the Science paper, and a theoretical astrophysicist and professor of physics and astronomy at Northwestern. "We now better understand the process of planet formation and can explain the properties of the strange exoplanets we've observed. We also know that the solar system is special and understand at some level what makes it special." Continue reading "Is Our Solar System a Rarity in Milky Way? Scientists Say "Yes"" »

Phoenix Mars lander 'tastes' first sample of water ice

• 22:38 31 July 2008
• NewScientist.com news service
• New Scientist Space and Reuters

Related Articles

• Phoenix lander uncovers ice on Mars
• 20 June 2008
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• 23 May 2008
• "Frozen ocean" under Mars surface
• 27 May 2002

Nasa's Lander samples Mars water

Nasa has completed a full panorama of the landing site

Nasa's Phoenix Lander spacecraft has for the first time identified water in a sample of soil collected from the planet's surface.

Scientists will now be able to begin studying the sample to see whether the planet was ever, or is, habitable.

The craft previously had problems transferring samples from its robotic arm to the onboard lab for analysis.

The success and the good condition of the craft mean the mission will be extended until the end of September.

Since it landed on June 25, the Phoenix Lander has been studying the surface of Mars to investigate whether it has ever been capable of supporting life.

It has been studying soil with a chemistry lab, an oven called TEGA [Thermal and Evolved-Gas Analyzer instrument], a microscope, a probe and cameras.

Scientists told a press conference at the University of Arizona in Tucson that the planet had so far "proved itself to be interesting".

William Boynton, lead scientist on the mission, said evidence of water ice had been seen before from the Mars Odyssey orbiter, but that this is the first time Martian water has been "touched and tasted".

Full panorama

Phoenix had collected some ice samples last week but was unable to transfer them from the mechanical scoop to the onboard oven for heating and testing.

A dry soil sample was taken instead but the scientists found some ice had been collected too and tests were being conducted on it.

The scientists said they had yet to find organic materials in the sample and stressed that it would take 3 to 4 weeks for the data to be analysed.

The 90-day extension to the mission means Nasa will be able to dig two new trenches between mountains where ice lasts for longer periods of time giving it different characteristics.

"Phoenix is healthy and the projections for solar power look good," said chief scientist Michael Meyer.

"We want to take full advantage of having this resource in one of the most interesting locations on Mars".

Nasa also announced the completion of a full panoramic image of the arctic landing site in approximate true colour.

The panorama is made up of more than 400 individual images taken over several weeks and stitched together to form a mosaic.

Phoenix carries seven science instruments

Life from Venus blown to Earth?

Temperatures on the surface of Venus can reach 464C (867F)

Life on Venus could be blown to Earth by powerful winds, scientists claim.

Previous research has considered the possibility of micro organisms existing in Venus's atmosphere despite extreme temperatures on its surface.

But two scientists at the Cardiff Centre for Astrobiology say microbes from Venus could actually be blown into the Earth's atmosphere by solar winds.

Their findings follow analysis of data from the European Space Agency's Venus Express probe, launched in 2005.

Prof Chandra Wickramasinghe and Dr Janaki Wickramasinghe claim

Venus's clouds contain chemicals that are consistent with the presence of micro organisms.

VENUS FACTS Distance from Sun: 108,200,000km Diameter: 12,103km Year length: 224.7 Earth days Atmosphere: 96% carbon dioxide, 3% nitrogen Moons: 0 Missions: Between 1961 and 1989 the US and USSR launched more than 30 spacecraft towards Venus Brightness: Venus is the brightest object in the sky apart from the Sun and Moon

They suggest that under certain conditions, these microbes from high in Venus's atmosphere could be blown into the Earth's atmosphere.

This process would only take days or weeks.

But

the Sun, Earth and Venus must be suitably aligned,

which last happened in 2004 and will not happen again until 2012.

Prof Wickramasinghe said: "Venus and Earth have often been referred to as sisters because of their geological similarities.

"Our research proposes that the two sisters may be biologically interconnected as well."

The work has been published online in a new paper in the Astrophysics and Space Science journal.

But Prof Fred Taylor, a planetary scientist at Oxford University, said

he was sceptical about the research.

"The idea of life on Venus, particularly the clouds where the temperature and pressure are similar to the Earth, has been floated around for a while but is not really very likely,"

he said.

He added that it was "most unlikely" anyway that microbes from Venus could be transferred to the Earth's atmosphere by solar winds.

The Venus Express probe, launched in November 2005, is orbiting the planet to study its atmosphere.

Scientists hope to learn how Venus, which is similar to Earth in size, mass and composition, evolved so differently over the last 4.6 billion years.

The mission was the first to be sent to the planet in 15 years.

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.

Researchers Discover Remnant of an Ancient 'RNA World'

by PhysOrg

Thanks to Cyberguy for the link.

http://www.physorg.com/news135522723.html

Researchers Discover Remnant of an Ancient 'RNA World'

(PhysOrg.com) -- Some bacterial cells can swim, morph into new forms and even become dangerously virulent - all without initial involvement of DNA. Yale University researchers describe Friday in the journal Science how bacteria accomplish this amazing feat - and in doing so provide a glimpse of what the earliest forms of life on Earth may have looked like.

To initiate many important functions, bacteria sometimes depend entirely upon ancient forms of RNA, once viewed simply as the chemical intermediary between DNA's instruction manual and the creation of proteins, said Ronald Breaker, the Henry Ford II Professor of Molecular, Cellular and Developmental Biology at Yale and senior author of the study.

Proteins carry out almost all of life's cellular functions today, but many scientists like Breaker believe this was not always the case and have found many examples in which RNA plays a surprisingly large role in regulating cellular activity. The Science study illustrates that - in bacteria, at least - proteins are not always necessary to spur a host of fundamental cellular changes, a process Breaker believes was common on Earth some 4 billion years ago, well before DNA existed.

"How could RNA trigger changes in ancient cells without all the proteins present in modern cells? Well, in this case, no proteins, no problem," said Breaker, who is also a Howard Hughes Medical Institute investigator.

Breaker's lab solved a decades-old mystery by describing how tiny circular RNA molecules called cyclic di-GMP are able to turn genes on and off. This process determines whether the bacterium swims or stays stationary, and whether it remains solitary or joins with other bacteria to form organic masses called biofilms. For example, in Vibrio cholerae, the bacterium that causes cholera, cyclic di-GMP turns off production of a protein the bacterium needs to attach to human intestines.

The tiny RNA molecule, comprised of only two nucleotides, activates a larger RNA structure called a riboswitch. Breaker's lab discovered riboswitches in bacteria six years ago and has since shown that they can regulate a surprising amount of biological activity. Riboswitches, located within single strands of messenger RNA that transmit a copy of DNA's genetic instructions, can independently "decide'' which genes in the cell to activate, an ability once thought to rest exclusively with proteins.

Breaker had chemically created riboswitches in his own lab and - given their efficiency at regulating gene expressions - predicted such RNA structures would be found in nature. Since 2002, almost 20 classes of riboswitches, including the one described in today's paper, have been discovered, mostly hidden in non-gene-coding regions on DNA.

"We predicted that there would be an ancient 'RNA city' out there in the jungle, and we went out and found it,'' Breaker said.

Bacterial use of RNA to trigger major changes without the involvement of proteins resolves one of the questions about the origin of life: If proteins are needed to carry out life's functions and DNA is needed to make proteins, how did DNA arise?

The answer is what Breaker and other researchers call the RNA World. They believe that billions of years ago, single strands of nucleotides that comprise RNA were the first forms of life and carried out some of the complicated cellular functions now done by proteins. The riboswitches are highly conserved in bacteria, illustrating their importance and ancient ancestry, Breaker said.

Understanding how these RNA mechanisms work could lead to medical treatments as well, Breaker noted. For instance, a molecule that mimics cyclic di-GMP could be used to disable or disarm bacterial infections such as cholera, he said.

Provided by Yale University

Water 'widespread' on early Mars

In Mars' Nili Fossae, clays are concentrated on slopes and along canyon walls

Water was once widespread on Mars, data from a Nasa spacecraft shows, raising the prospect that the Red Planet could have supported life.

Researchers found evidence of vast lakes, flowing rivers and deltas on early Mars, all of which were potential habitats for microbes.
They also discovered that wet conditions probably persisted for a long time on the Red Planet.
Details appear in the journals Nature and Nature Geoscience.

It wasn't this hot, boiling cauldron. It was a benign, water-rich environment for a long period of time Jack Mustard, Brown University

One study shows that vast regions of Mars' ancient highlands, which cover about half the planet, contain clay minerals - which can form only in the presence of water.

Volcanic lavas buried the clay-rich regions during subsequent, drier periods of the planet's history, but impact craters later exposed them at thousands of locations across Mars.
The data comes from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument on the US space agency's Mars Reconnaissance Orbiter spacecraft.
CRISM works by "reading" over 500 colours in reflected sunlight to detect particular minerals on the Martian surface - including those that formed in the presence of water.
"The big surprise from these new results is how pervasive and long-lasting Mars' water was, and how diverse the wet environments were," said Crism's chief scientist Scott Murchie, from the Johns Hopkins University Applied Physics Laboratory in Maryland.
Cosmic bombardment
The clay minerals, known as phyllosilicates, preserve a record of the interaction of water with rocks dating back to the Noachian period of Martian history, which lasted from about 4.6 billion years ago to 3.8 billion years ago.
This was a time in which the Earth, the Moon and Mars were being pummelled by comets and asteroids.

Rivers once flowed into Mars' Jezero Crater, carrying clay minerals

Rocks of this age have largely been destroyed on Earth by plate tectonics. They are preserved on the Moon, but were never exposed to liquid water. So rocks containing phyllosilicates on Mars preserve a unique record of watery environments in the early Solar System, some of which could have been stable long enough for life to get started.
Importantly, CRISM detected hydrated silicates - so called because they contain water in their crystalline structure - within sediments that had been clearly deposited by water.
The clay minerals were found in fans and deltas within the Holden, Eberswalde and Jezero craters on Mars.
"In most locations the rocks are lightly altered by liquid water, but in a few locations they have been so altered that a great deal of water must have flushed though the rocks and soil," said Jack Mustard, professor of planetary geology at Brown University in Rhode Island.
"This is really exciting because we're finding dozens of sites where future missions can land to understand if Mars was ever habitable and if so, to look for signs of past life."
Deep and cool
The European and US space agencies have targeted several phyllosilicate-rich regions as potential landing sites for their next rover missions to Mars.

MSL LANDING SITE SHORTLIST Nili Fossae Trough - 25km-wide linear trough with exposed clays and volcanic deposits Holden Crater - 150km-wide crater once filled by a lake which experienced a massive flood Mawrth Vallis - Valley with many exposed, clays deposited over a long time Eberswalde Crater - 65km-wide depression once filled with water and featuring an ancient delta Northern Meridiani - Region at equator rich in minerals that typically form in presence of water Miyamoto Crater - Impact depression in Meridiani region with exposed clay minerals

The team also found phyllosilicate deposits in thousands of places in and around craters, including the pointed peaks located at the centres of some impact depressions. This example suggests that water was present 4-5km below the ancient Martian surface, the researchers said.
Crater-causing collisions are thought to have excavated underground minerals that were then exposed on the crater peaks.
"Water must have been creating minerals at depth to get the signatures we see," Professor Mustard explained.
The clay minerals must have been formed at relatively low temperatures.
"What does this mean for habitability? It's very strong," explained Professor Mustard.
"It wasn't this hot, boiling cauldron. It was a benign, water-rich environment for a long period of time."
In a separate study published in the journal Nature Geoscience, a team led by Bethany Ehlmann, from Brown University, analysed sedimentary deposits in two deltas within Mars' Jezero crater - which once hosted a body of water measuring some 40km (25 miles) across.
The deltas suggest a river transported clay minerals into the basin from a watershed.
"Not only was water active in this region to weather the rocks, but there was enough of it to run through the beds, transport the clays and run into the lake and form the delta," said Ms Ehlmann.
She added that the deltas appeared to be excellent candidates for finding stored organic matter, because the clays brought in from the watershed and deposited in the lake would have trapped any organisms, leaving a "cemetery of microbes".
Nasa will send a robotic rover, Mars Science Laboratory (MSL), to the planet in September 2009 to look for signs of past or present life.
The European Space Agency (Esa) also plans to send a rover to investigate Mars' habitability. This mission, called ExoMars, is scheduled to launch in 2013.

Mars probe makes 'ice discovery'

Tiny clumps of material in the bottom left of the trench on 15 June (left) are gone by 19 June (right) Enlarge Image

Nasa's Phoenix lander has unearthed compelling evidence of ice on Mars, mission scientists believe.

Chunks of a bright material found in a trench dug by the craft have disappeared over four Martian days, suggesting they have vapourised.

While digging in another trench, the lander's arm connected with a hard surface at the same depth.

The finds lend weight to suggestions water is locked up in a permafrost layer close to the planet's surface.

Missing matter

"It must be ice,"

said Dr Peter Smith, Phoenix's principal investigator, who is based at the University of Arizona, Tucson.

"These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice," he said.

"There had been some question whether the bright material was salt," he added.

"Salt can't do that."

The dice-sized chunks were unearthed in a trench informally known as Dodo-Goldilocks, which Phoenix dug and photographed on the 20th day of its stay on Mars.

Four days later when the trench was snapped again, some of the chunks had disappeared.

Earlier in the mission hopes of discovering ice were fading as soil samples scooped up earlier by Phoenix yielded no trace of water.

While evidence of ice on Mars has been gathered before, part of Phoenix's mission is to search out evidence to support the idea that the polar region of the planet could be habitable.

'Same depth'

Further confirmation of the ice theory came from another trench, known as Snow White 2.

Digging there was halted when the scraper on the lander's robotic arm hit a hard surface just under the soil layer.

"We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench," said Ray Arvidson of Washington University in St Louis, who is lead scientist for the robotic arm.

The arm also stopped three times earlier while digging in a "polygon".

This automatic reaction is a programmed response triggered when the scoop hits a hard, sub-surface region.

"Polygons" are soil features seen on Earth when permafrost layers in soil expand and contract as temperatures rise and fall.

Phoenix now seems to have confirmed that similar features on Mars are caused by the same processes as those on this planet.

Trio of 'super-Earths' discovered

The planets are rocky worlds between two and 10 times the size of Earth

Astronomers have identified a trio of so-called "super-Earths" - rocky planets between two and 10 times the mass of Earth.

The three new planets were detected using the Harps instrument at the La Silla Observatory in central Chile.

The star they circle is slightly smaller than our Sun, and is located 42 light-years away near the southern Doradus and Pictor constellations.

The discoveries were announced at an astronomy conference in Nantes, France.

When a planet orbits its star, it exerts a gravitational pull which causes the parent star to "wobble" around its centre of mass.

The High Accuracy Radial velocity Planet Searcher (Harps) spectrograph was able to measure this wobble to a very high precision over a period of five years.

This was vital because the perturbations caused by the planets were tiny.

"The mass of the smallest planet is one hundred thousand times smaller than that of the star," said co-author Francois Bouchy, from the Astrophysics Institute of Paris, France.

Chances are

The new worlds, which circle the star HD 40307, are 4.2, 6.7 and 9.4 times the size of Earth. They are named super-Earths because they are more massive than the Earth but less massive than Uranus and Neptune (which are about 15 Earth masses).

Using Harps data, the astronomers also counted a total of 45 candidate planets with a mass below 30 Earth masses.

This implies that one solar-like star out of three harbours such planets.

Astronomer Michel Mayor from the Geneva Observatory in Switzerland commented: "Does every single star harbour planets and, if yes, how many?

"We may not yet know the answer but we are making huge progress towards it."

Since the discovery in 1995 of a planet around the star 51 Pegasi by Michel Mayor and his colleague Didier Queloz, more than 270 exoplanets have been found - mostly around Sun-like stars.

The majority of these planets are gas giants, a bit like Jupiter or Saturn in our own Solar System. Current data shows that about one in 14 stars harbours this kind of planet.

The Harps instrument is attached to the La Silla 3.6m telescope in Chile. The facility is run by the European Southern Observatory (Eso) organisation.

Scientists confirm that parts of earliest genetic material may have come from the stars

by Eurek Alert

Thanks to Richard Prins for the link.

http://www.eurekalert.org/pub_releases/2008-06/icl-sct061308.php

Scientists confirm that parts of earliest genetic material may have come from the stars

Scientists have confirmed for the first time that an important component of early genetic material which has been found in meteorite fragments is extraterrestrial in origin, in a paper published on June 15, 2008

The finding suggests that parts of the raw materials to make the first molecules of DNA and RNA may have come from the stars.

The scientists, from Europe and the USA, say that their research, published in the journal Earth and Planetary Science Letters, provides evidence that life's raw materials came from sources beyond the Earth.

The materials they have found include the molecules uracil and xanthine, which are precursors to the molecules that make up DNA and RNA, and are known as nucleobases.

The team discovered the molecules in rock fragments of the Murchison meteorite, which crashed in Australia in 1969.

They tested the meteorite material to determine whether the molecules came from the solar system or were a result of contamination when the meteorite landed on Earth.

The analysis shows that the nucleobases contain a heavy form of carbon which could only have been formed in space. Materials formed on Earth consist of a lighter variety of carbon.

Lead author Dr Zita Martins, of the Department of Earth Science and Engineering at Imperial College London, says that the research may provide another piece of evidence explaining the evolution of early life. She says:

"We believe early life may have adopted nucleobases from meteoritic fragments for use in genetic coding which enabled them to pass on their successful features to subsequent generations."

Between 3.8 to 4.5 billion years ago large numbers of rocks similar to the Murchison meteorite rained down on Earth at the time when primitive life was forming. The heavy bombardment would have dropped large amounts of meteorite material to the surface on planets like Earth and Mars.

Co-author Professor Mark Sephton, also of Imperial's Department of Earth Science and Engineering, believes this research is an important step in understanding how early life might have evolved. He added:

"Because meteorites represent left over materials from the formation of the solar system, the key components for life -- including nucleobases -- could be widespread in the cosmos. As more and more of life's raw materials are discovered in objects from space, the possibility of life springing forth wherever the right chemistry is present becomes more likely."

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For further information please contact:

Colin Smith
Press Officer
Imperial College London
Email: cd.smith@imperial.ac.uk
Tel: +44 (0)207 594 6712
Out of hours duty press officer: +44 (0)7803 886 248

Dr Zita Martins
Department of Earth Science and Engineering
South Kensington Campus
Imperial College London
London SW7 2AZ, UK
Tel: +44 (0)20 7594 9982
Fax: +44 (0)20 7594 7444
Email: z.martins@imperial.ac.uk
http://www.imperial.ac.uk/people/z.martins

Notes to editors:

1. "Extraterrestrial nucleobases in the Murchison meteorite", Earth and Planetary Science Letters, Sunday 15 June 2008 (Print publication)

A full copy of the research can be downloaded at: http://dx.doi.org/10.1016/j.epsl.2008.03.026

Mars lander is 'in good health'

Polygon patterns are similar to those in permafrost regions on Earth

Nasa says its Phoenix spacecraft is in good health after making the first successful landing in the north polar region of Mars.

Images sent back show a flat valley floor with polygonal features that give the ground a "paved" appearance.

These are believed to be a sign of the water-ice that lies just beneath the surface at these high latitudes.

The ice should be within reach of the probe's 2.35m-long robotic arm, which is due to be deployed this week.

The arm can dig through the topsoil to the ice beneath and scoop up samples to return to the lander's deck for analysis.

Phoenix is set to investigate the planet's geological history and search for the chemical building blocks which could support life.

The polygons seen in the latest images have previously been spotted from space and are thought to be caused by expansion and contraction of ice. Similar features can be seen in permafrost regions on Earth.

A Nasa orbiter took this image of Phoenix parachuting to the surface

"We see the lack of rocks that we expected, we see the polygons that we saw from space, we don't see ice on the surface, but we think we will see it beneath the surface. It looks great to me," said Professor Peter Smith, principal investigator for the Phoenix mission.

But Professor Smith also mentioned that the polygons were smaller than expected.

Some scientists think there may be a large-scale polygonal structure to the Martian surface as seen from space. But from the ground, it seems there are polygons within polygons.

This suggests that water-ice could lie very near the surface indeed: the closer it is to the surface, the more fractured it becomes, leading to smaller polygon shapes.

A signal confirming the lander had reached the surface was received at 2353 GMT on 25 May (1953 EDT; 0053 BST on 26 May).

Engineers and scientists at Nasa's Jet Propulsion Laboratory (JPL) in California clapped and cheered when the landing signal came through.

Soft landing

The final seven minutes of the probe's 10-month journey to Mars were regarded as the hardest part of the mission.

The probe had to survive a fiery plunge through the planet's thin atmosphere, slowing from a speed of nearly 21,000km/h (13,000 mph).

It released a parachute, used pulsed thrusters to slow to a fast-walking speed, and then descended the last few metres to the Martian soil to land on three legs.

The Nasa team monitored each stage of the descent and landing process through radio messages relayed to Earth via the Odyssey satellite in orbit around Mars.

Phoenix carries seven science instruments

Nasa found out more about the landing when pictures from the probe reached the Earth.

The first pictures confirmed that the solar arrays needed for the mission's energy supply had unfolded properly, and masts for the stereo camera and weather station had swung into their correct vertical position.

HOW PHOENIX LANDED

Phoenix lander craft jettisons cruise- stage power equipment seven minutes before reaching Mars' atmosphere.

Phoenix approaches Mars' atmosphere at 21,000km/h. The heat shield can withstand temperatures of 1,420C.

About 13km above Mars' surface, Phoenix deploys its parachute and the heat shield is jettisoned.

Radar is activated providing information to the onboard computer, which will calculate final descent.

Lander separates from back shell. Radar and thrusters guide Phoenix to a clear landing.

Over the next three months, Phoenix will analyse the planet’s icy soil to see if life could survive on Mars.

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"Seeing these images after a successful landing reaffirmed the thorough work over the past five years by a great team," said the mission's project manager Barry Goldstein, from JPL.

The spacecraft will begin its three-month science mission in the next few days.

Phoenix is an apt name for the current mission, as it rose from the ashes of two previous failures.

In September 1999, the Mars Climate Orbiter spacecraft crashed into the Red Planet following a navigation error caused when technicians mixed up "English" (imperial) and metric units.

A few months later, another Nasa spacecraft, the Mars Polar Lander (MPL), was lost near the planet's South Pole.

Phoenix uses hardware from an identical twin of MPL, the Mars Surveyor 2001 Lander, which was cancelled following the two consecutive failures.

The probe was launched on 4 August 2007 on a Delta II rocket from Cape Canaveral Air Force Station in Florida.

Phoenix landed further north than previous missions

The Drake Equation = Number of Detectable Civilisations in Our Galaxy

Work out for yourself aided by the brilliant BBC 'Horizon' programme videos on the Drake Equation the number of Detectable Intelligent Civilisations (N) in the Milky Way Galaxy.

Drake Equation: N = Rs x Fp x Ne x Fl x Fi x Fc x L

I calculate (my maths is probably wrong!) that the possible range is huge: there may be many billions or only one Detectable Intelligent Civilisation (us!) in the known Universe. My calculations of the worst and best cases for Detectable Intelligent Civilisation are based on the estimates given in the BBC 'Horizon' video.

• Rs = rate of star formation (20 per year)
  
• 20 per year x 10 billion years = 200,000,000,000 = 200 billion stars in our Milky Way galaxy
  
• Fp = fraction of stars with planetary systems (0.1)
  
• 0.1 x 200 billion stars = 20 billion
  
• Ne = average number of planets which could support life per star with planets = 0.2 to 0.4
  
• 8 billion (20 billion x 0.4) best case
• 4 billion (20 billion x 0.2) worst case
• Fl = fraction of earth like planets that contain life = 0.9 to 1 x 10-6
  
• 7.2 billion (8 billion x 0.9) best case
• 4000 (4 billion/1 million) worst case
• Fi = fraction of planets that contain life that evolves into intelligent life = 0.5 to 1 x 10-6 (1 in a million)
• 3.6 billion (7.2 billion x 0.5) best case
• 0.004 (4000/1,000,000) worst case
• Fc = fraction of worlds that develop science and technology = 1 (best case) to 1 x 10-3 (worst case)
  
• 3.6 billion (3.6 billion x 1) best case
• 0.000004 (0.004/1000) worst case
• L = longevity of civilisation (years) / Age of Galaxy = 0.01 (100 million /10 billion) (best case) to (100/10 billion) 0.000000001 (100/10 billion) (worst case)
  
• N = 3.6 x 10 power 7 = 36 million (3.6 billion x 0.01) best case
• N = 4 x 10 power minus 13 (0.000004 x 0.000000001) worst case
• N (universe) best case = 3.6 x 10 power 17 (3.6 x 10 power 7 x 100 billion (10 power 11)
  
• N (universe) worst case = 1 civilisation (4 x 10 power minus 13 x 100 billion (1 x 10 power 11 galaxies)

Other information: wikipedia Drake Equation

Solar System's 'look-alike' found

By Paul Rincon Science reporter, BBC News, Belfast

Almost 300 planets have now been found outside our Solar System

Astronomers have discovered a planetary system orbiting a distant star which looks much like our own.

They found

two planets that were close matches for Jupiter and Saturn orbiting a star about half the size of our Sun.

Martin Dominik, from St Andrews University in the UK, said the finding suggested systems like our own could be much more common than we thought.

And he told a major meeting that astronomers were on the brink of finding many more of them.

The St Andrews researcher said

this planetary system, and others like it, could host terrestrial planets like Earth.

It was just a matter of time before such worlds were detected, he explained.

Dr Dominik told BBC News: "We found a system with two planets that take the roles of Jupiter and Saturn in our Solar System. These two planets have a similar mass ratio and similar orbital radius and a similar orbital period.

"It looks like this may have formed in a similar way to our Solar System. And if this is the case, it looks like [our] Solar System cannot be unique in the Universe. There should be other similar systems out there which could host terrestrial planets."

Dr Dominik presented his work at the Royal Astronomical Society's National Astronomy Meeting in Belfast.

Ultimate goal

The newfound planetary system, which orbits the star OGLE-2006-BLG-109L, is more compact than our own and is about five thousand light-years away. (Astrophysics - Science journal - Feb 2008 - Full Article pdf)

Although nearly 300 extrasolar planets have been identified, astronomers have consistently failed to find planetary systems which resemble our own. Dr Dominik said only 10% of systems discovered so far are known to host more than one planet.

But he explained that all the

techniques currently used to find exoplanets were strongly biased towards detecting gas giant planets orbiting at short distances from their parent stars.

The OGLE (Optical Gravitational Lensing Experiments) planets were found using a technique called Gravitational Microlensing, in which light from the faraway planets is bent and magnified by the gravity of a foreground object, in this case a another star.

"It's a kind of scaled-down version of our Solar System. The star the planets are orbiting is half as massive as the Sun and they orbit half as distant to their host star as Jupiter and Saturn orbit around the Sun," said Dr Dominik.

He said that

the ultimate goal for exoplanet researchers was to find habitable Earth-like and Mars-like planets. This aim was achievable, he said, because technology was improving all the time.

"I think it will happen quite soon," he said, adding: "Micro-lensing can already go below Earth mass and it has detected more massive planets in the habitable zone. So in the next few years, we will see something really exciting."

Dr Dominik said there was competition between teams of astronomers using micro-lensing and those who favoured the transit technique, which seeks to detect new planets when, from our point of view, they pass directly in front of the parent star they are orbiting. The planet blocks a tiny fraction of the star's light, causing the star to periodically dim.

But he added that there was little chance to detect Earth-like worlds in OGLE-2006-BLG-109L because the system was too distant for current techniques to resolve planets the size of our own.

Saturn moon may have hidden ocean

Saturn moon may have hidden ocean

By Helen Briggs Science reporter, BBC News

Future observations by Cassini will help test the prediction

Saturn's moon Titan may have a deep, hidden ocean, according to data published in the journal Science.

Radar images from the Cassini-Huygens mission reinforce predictions that a reservoir of liquid water exists beneath the thick crust of ice.

If confirmed, it would mean that Titan has two of the key components for life - water and organic molecules.

Currently, three other Solar System objects are suspected of having deep oceans: Ganymede, Callisto and Europa.

The Cassini-Huygens mission is a cooperative project of the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).

We've got to go back again with balloons and rovers and really understand this place Prof John Zarnecki

When Cassini began to observe the largest of Saturn's moons in 2004, the surface was thought to be completely covered with an ocean of hydrocarbons.

But when the spacecraft turned its radar on the moon for the first time in 2004, and the Huygens probe parachuted to the surface a year later, a different picture emerged.

Much of the surface was found to be solid, with geological features such as dunes, channels and impact craters, punctuated by vast "lakes".

Cassini's latest fly-by of Titan is providing a new glimpse of these features, which to researchers' surprise, are not in the place they should be.

Scientists would like to send an instrumented balloon to Titan

Coupled with models of how the moon spins, the data suggests that the observed seasonal variation in spin rate could only exist if a liquid ocean lay beneath the solid crust.

The researchers, led by Dr Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory, US, say their predictions can be checked in the proposed extended Cassini mission or in future missions.

John Zarnecki, Professor of Space Science, at the UK's Open University, who was not part of the study, said the motivation to go back to Titan with a more sophisticated space probe was "overwhelming".

Evidence suggests that Titan has two of the key constituents for the formation of life - water and organic molecules, and possibly a third - a source of energy, he said.

Prof Zarnecki told BBC News: "We know there are organic molecules, the place is swarming in organics.

Titan: The second largest moon in the Solar System

"Titan is 50% water-ice. If it is liquid, as this paper is implying some of it is, it looks as though we've got at least two of the things to initiate the chemistry that leads to life.

"It wouldn't be too far fetched to imagine certain spots on Titan where there would be a source of energy - maybe geothermal energy, as we have on Earth at the bottom of the oceans."

Titan is the second largest moon in the Solar System; only Jupiter's Ganymede satellite is bigger.

Past observations have shown that

Titan in many ways resembles a very early Earth, particularly in the composition of its atmosphere. The major difference is the frigid temperatures out near Saturn.

Prof Zarnecki added: "We've got to go back again with balloons and rovers and really understand this place."