Could We Detect Plants on other Planets?

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We’ve already found over 250 extrasolar planets, and more are continuing to be discovered fairly often. With all of these new planets popping up, the obvious question must be asked: how do we go about detecting whether or not they contain life? Though we can’t yet see features on the surface with even the most powerful of telescopes – and probably won’t be able to do so for a very long time – an analysis of the light coming from the planet may reveal if it is covered with life in the form of plants.

Dr. Luc Arnold of the CNRS Observatoire de Haute-Provence in France suggests that a spectral analysis of the light reflected off of a planet could determine whether or not it is covered with vegetation.

Earth’s plant-covered surface absorbs certain frequencies of light, and reflects others. Our vegetation has a very specific spectrum because it absorbs a lot of visible light around 700 nanometers, or the color we see as red. This is called the Vegetation Red Edge (VRE).

By looking at the sunlight that is reflected off of the Earth – Earthshine – the composition of the Earth’s surface and atmosphere can be determined. The Earth’s light can be analyzed when it is reflected off of the Moon, or from spacecraft distant enough from the Earth to see it as a small disk.

Knowing the composition of the Sun’s light, and adjusting for the elements and minerals in the atmosphere and on the surface, there is still between 0-10% of the photons near the red end of the visible spectrum that are missing. The factor needed to explain this photon absorption is the presence of plants, which use the light for photosynthesis

This same method could potentially be used to detect the presence of vegetation on extrasolar planets, proposes Dr. Arnold in a paper titled, Earthshine Observation of Vegetation and Implication for Life Detection on Other Planets published in the October 30th, 2007 edition of the journal Space Science Review.

“The point is that if, in the spectrum of an Earthlike planet, we find a spectral signature –probably different than the VRE – that cannot be explained as a mineral signature, nor an atmospheric signature, then the proposition that this feature is a possible signature of life becomes relevant. Especially if a variation in the strength of the signal is correlated with planet’s rotation period, suggesting that the spectral feature is on planet’s surface,” Dr. Arnold said.

The VRE on Earth is calculated by taking out “noise factors” such as the composition of the atmosphere, whether there are a lot of clouds, and whether the part of the Earth reflecting the light is covered by desert, ocean, or forest. All of these things absorb light in different parts of the spectrum. These same details must be sorted out for other planets to ensure that the absence of photons in a certain part of the spectrum is indeed due to plants absorbing the light.

To be able to rule out other factors in the spectrum of the planet, the resolution has to be better than is currently possible. ESA’s Darwin and NASA’s Terrestrial Planet Finder, both missions being designed to specifically look for new terrestrial planets and better study already-discovered ones, are expected to launch in the next 10 years or so. They will not be able to resolve the spectrum of extrasolar planets well enough to use this method for finding vegetation, but the second-generation of planet-finding telescopes will likely have this ability.

The question remains as to whether plants on distant worlds will use chlorophyll as their means of photosynthesizing light. Will the light they absorb be red, or a different color? Will the light they reflect be green or something completely bizarre, like magenta or bright blue? If they do use chlorophyll, their spectrum will be similar to that of our own planet. If not, their spectral signature may be rather different than that of Earth’s vegetation.

Dr. Arnold says a different VRE might still be rather interesting: “What would we say to us such a strange and different VRE ? It will reveal missing photons, i.e. photons form the star absorbed and ‘used’ (their energy) in an unknown or unidentified chemical process, that’s all we would learn. Here again, other information about the atmosphere composition (water vapor, oxygen, ozone, etc.) and temperature would help to make coherent proposals. At least it would feed an very exciting debate!”

Source: Space Science Review

These are Tough Microbes, But They Don’t Come from Mars

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You know the cliche, wherever we find water here on Earth, we find life. But what if the environment is really hostile? So hostile that any living creature would almost never see water. And even when there was water, they were constantly being blasted with radiation. Amazingly, there’s a microbe out there, Deinococcus geothermalis, that can handle some of the harshest environments on the planet – favoured habitats include nuclear power plants. Scientists once suspected that microbes like this might have evolved on Mars. Nope, they’re homegrown.

Of all the different strains of bacteria on Earth, those in the genus Deinococcus are a hardy bunch. They’re extremely resistant to ionizing radiation, they laugh at ultraviolet light, extreme, heat, cold and they don’t mind being completely dried out for long periods. Bathed in acid? Boring.

D. geothermalis is actually a cousin of another microbe called Deinococcus radiodurans. D. radiodurans is capable of withstanding 500 times the radiation that will kill a human – with no loss of viability. The Guiness Book of World records calls D. radiodurans the toughest bacteria in the world, and some scientists have proposed that it actually evolved on Mars and somehow journeyed to Earth.

Researchers have recently sequenced the bacteria’s cousin, D. geothermalis’ entire genome sequence, providing some valuable clues into how a microbe can be so tough, and how they two are related (no Martian explanation necessary).

Their paper describing the results of their sequencing efforts, entitled Deinococcus geothermalis: The Pool of Extreme Radiation Resistance Genes Shrinks will be published in the September 26th issue of the journal Public Library of Science.

The microbe was first discovered in a hot pool at the Termi di Agnano, in Naples, Italy. Other scientists have turned it up in other nasty locations, such as industrial paper machine water, deep ocean subsurface environments, and subterranean hot springs in Iceland.

While working with the microbe, the researchers noted, “the extraordinary survival of Deinococcus bacteria following irradiation has also given rise to some rather whimsical descriptions of their derivation, including that they evolved on Mars.”

In fact, the US Department of Energy is considering D. geothermalis as a possible solution to break down radioactive waste. Which would be good, since it’s often a pest; adhering to the surface of steel, and causing problems in nuclear power plants.

Currently, scientists have no idea why bacteria like D. geothermalis are so hardy to radiation. They’re just as susceptible to normal bacteria to have their DNA broken up by radiation, but they use some kind of efficient repair mechanism to fix the damage quickly.

The big surprise with this research is that it overturns previously held theories about how D. radiodurans protects itself. The two strains of bacteria are both extremely resistant to radiation, and yet D. geothermalis lacks the genes that scientists thought D. radiodurans was using. By comparing genome sequences between the two strains, the researchers were able to narrow down the genes which are likely contributing to the microbes’ tolerance.

This research also overturns the intriguing possibility that D. radiodurans comes from Mars; evolving on the Cosmic Ray blasted surface of the Red Planet. These two strains have enough in common, with traceable evolutionary steps, that the researchers can see how they evolved right here on Earth.

Here’s Dr. Michael J. Daly, an associate professor at the Uniformed Services University of the Health Sciences in Bethesda, “the thermophile Deinococcus geothermalis is an excellent organism in which to consider the potential for survival and biological evolution beyond its planet of origin, as well as the ability of life to survive extremely long periods of metabolic dormancy in high-radiation environments. The current work reinforces the notion that resistance to radiation and desiccation readily evolved on Earth, and that the underlying resistance systems are based on a universal set of repair genes. The work underscores the vulnerability of potential life-inhabiting environments on Mars to contamination by human exploration; and how the efficiency of ordinary DNA repair proteins could be increased, which might be important to astronauts. The growing awareness that there is hardly a habitat on Earth not harboring life is now changing our consensus of consequences for possible life on Mars.”

Sorry Mars, go evolve your own microbes.

Original Source: PLOS Journal article

Dangerous Microbes Toughen Up in Space

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Well this news can’t be good. While human bodies tend to get weaker during long duration spaceflight, dangerous microbes just get feistier, returning to Earth even more infectious. A colony of Salmonella typhimurium, the main culprit in food poisoning, flew aboard the space shuttle Atlantis last year. They came back three times more likely to cause disease when compared to control bacteria on the ground.

The discovery was made by researchers from Arizona State University’s Biodesign Institute. Back in September 2006, they included a special experiment flown during the space shuttle Atlantis’ mission STS-115. Don’t worry, the bacteria were placed in three layers of containment to keep the crew safe. At the same time, a control experiment was maintained here on Earth.

The microbes were activated when they were pushed into a special growth chamber containing the nutrients they needed to multiply. They grew for 24 hours, and then astronaut Heidemarie M. Stefanyshyn-Piper pushed a plunger on the experiment that halted their growth, and preserved them. Another group of bacteria got fresh nutrients, so they could continue to grow and multiply.

Once the bacteria were returned to Earth, researchers measured the bacteria’s gene and protein expression, and calculated their virulence. They found that the space traveling bacteria had changed expression of 167 genes. And they found that the bacteria was 3 times as likely to cause disease in animals (we probably don’t want to know how they tested this) as the bacteria grown on the ground.

Why is this happening? The scientists aren’t sure. They have ruled out the near zero-gravity, though. Their best explanation is a poorly understood phenomenon called fluid shear. This is the force of liquid passing over the cells. In microgravity, this fluid shear is very low, similar to the environment of the gastrointestinal track.

As frightening as this sounds, there should be a silver lining here. Salmonella is a particularly nasty strain of bacteria. Learning how it responded to spaceflight should give researchers valuable clues to how it grows and generates its dangerous toxin.

Original Source: ASU News Release

Life Marker Chip Heads to Space

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Would you know microbial life if you saw it? What if you were a robot? A newly developed “Life Marker Chip” might give future robotic explorers a tool they can use to know if the rock, sand, water or ice they’re examining contains life. This device, as well as a few dozen other experiments recently headed to space aboard the Foton microgravity mission.

The unmanned Soyuz-U launcher blasted off from the Kaikonur Cosmodrome, Kazakhstan on September 14th. 9 minutes after launch, the Foton-M3 spacecraft separated from the rocket’s upper stage, and went into an orbit that takes it around the Earth every 90 minutes.

The spacecraft is carrying a payload of 43 experiments designed to test the effects of microgravity and radiation. The experiments include fluid physics, biology, protein crystal growth, meteoritics, radiation dosimetry and exobiology. And one interesting member of the mission is the Life Marker Chip.

The nickname for the Life Marker Chip is the Mars pregnancy test since it works on the same principle. It contains a tray of very specific proteins, each of which acts like a plug. If microbial life is present on Mars, some of its protein molecules will come into contact with the LMC, and then bond, like a very specific puzzle piece. This will allow the robot to not only report on evidence of life, but give very specific information about what kind of life process is being observed.

The trip to space on board the Foton is just a test. Scientists want to see what happens to the experiment when it’s exposed to the radiation and microgravity of being in orbit. The experiment, as well as the other 40ish experiments on board the capsule will be recovered when the capsule returns to Earth on September 25th.

If everything works properly, the Life Marker Chip will be installed onto ESA’s ExoMars mission; a rover that will blast off for the Red Planet in 2013. Maybe then we’ll get the answer we’re hoping for: Mars is pregnant… with life.

Original Source: Carnegie Institution News Release

Podcast: Panspermia

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As a reward to the all the dedicated fans who completed our demographic survey, we released this special episode of Astronomy Cast. As promised, we’re now releasing this episode to all of our subscribers. Panspermia is a controversial theory that life on Earth originated… out there. Maybe it started out in a cosmic dust cloud or originated from another planet, but somehow the very first lifeforms made the trip through the vacuum of space and colonized our home planet.

Click here to download the episode

Panspermia – Show notes and transcript

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A Submarine for Europa

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Many planetary scientists believe that Jupiter’s moon Europa is our solar system’s best contender to share Earth’s distinction of harboring life. Evidence gathered by the Voyager and Galileo spacecrafts suggests Europa contains a deep, possibly warm ocean of salty water under an outer shell of fissured ice. In a paper published in the July 2007 Journal of Aerospace Engineering a British mechanical engineer proposes sending a submarine to explore Europa’s oceans.

Carl T. F. Ross, a professor at the University of Portsmouth in England offers an abstract design of an underwater craft built of a metal matrix composite. He also provides suggestions for suitable power supplies, communication techniques and propulsion systems for such a vessel in his paper, “Conceptual Design of a Submarine to Explore Europa’s Oceans.”

Ross’s paper weighs the options for constructing a submarine capable of withstanding the undoubtedly high pressure within Europa’s deep oceans. Scientists believe that this moon’s oceans could be up to 100 kilometers deep, more than ten times deeper than Earth’s oceans. Ross proposes a 3 meter long cylindrical sub with an internal diameter of 1 meter. He believes that steel or titanium, while strong enough to withstand the hydrostatic pressure, would be unsuitable as the vessel would have no reserve buoyancy. Therefore, the sub would sink like a rock to the bottom of the ocean. A metal matrix or ceramic composite would offer the best combination of strength and buoyancy.

Ross favors a fuel cell for power, which will be needed for propulsion, communications and scientific equipment, but notes that technological advances in the ensuing years may provide better sources for power.

Ross concedes that a submarine mission to Europa won’t occur for at least 15-20 years. Planetary scientist William B. McKinnon agrees.
Artist illustration of a Europa probe. Image credit: NASA/JPL
“It is difficult enough, and expensive, to get back to Europa with an orbiter, much less imagine a landing or an ocean entry,” said McKinnon, professor of Earth and Planetary Sciences at Washington University in St. Louis, Missouri. “Sometime in the future, and after we have determined the ice shell thickness, we can begin to seriously address the engineering challenges. For now, it might be best to search for those places where the ocean has come to us. That is, sites of recent eruptions on Europa’s surface, whose compositions can be determined from orbit.”

The Jet Propulsion Laboratory is currently working on a concept called the Europa Explorer which would deliver a low orbit spacecraft to determine the presence (or absence) of a liquid water ocean under Europa’s ice surface. It would also map the distribution of compounds of interest for pre-biotic chemistry, and characterize the surface and subsurface for future exploration. “This type of mission,” says McKinnon, “would really allow us to get the hard proof we would all like that the ocean is really there, and determine the thickness of the ice shell and find thin spots if they exist.”

McKinnon added that an orbiter could find “hot spots” that indicate recent geological or even volcanic activity and obtain high-resolution images of the surface. The latter would be needed to plan any successful landing.

Slightly smaller than Earth’s moon, Europa has an exterior that is nearly craterless, meaning a relatively “young” surface. Data from the Galileo spacecraft shows evidence of near-surface melting and movements of large blocks of icy crust, similar to ice bergs or ice rafts on Earth.

While Europa’s midday surface temperatures hover around 130 K (-142 C, -225 degrees F), interior temperatures could be warm enough for liquid water to exist underneath the ice crust. This internal warmth comes from tidal heating caused by the gravitational forces of Jupiter and Jupiter’s other moons which pull Europa’s interior in different directions. Scientists believe similar tidal heating drives the volcanoes on another Jovian moon, Io. Seafloor hydrothermal vents have also been suggested as another possible energy source on Europa. On Earth, undersea volcanoes and hydrothermal vents create environments that sustain colonies of microbes. If similar systems are active on Europa, scientists reason that life might be present there too.

Among scientists there is a big push to get a mission to Europa underway. However this type of mission is competing for funding against NASA’s goal of returning to our own moon with human missions. The proposed Jupiter Icy Moon Orbiter (JIMO) a nuclear powered mission to study three of Jupiter’s moons, fell victim to cuts in science missions in NASA’s Fiscal Year 2007 Budget.

Ross has been designing and improving submarines for over 40 years, but this is the first time he’s designed a craft for use anywhere but on Earth.

“The biggest problem that I see with the robot submarine is being able to drill or melt its way through a maximum of 6 km of the ice, which is covering the surface,” said Ross. “However, the ice may be much thinner in some places. It may be that we will require a nuclear pressurized water reactor on board the robot submarine to give us the necessary power and energy to achieve this”

While Ross proposes using parachutes to bring the submarine to Europa’s surface, McKinnon points out that parachutes would not work in Europa’s almost airless atmosphere.

Ross has received very positive responses to his paper from friends and colleagues, he says, including notable British astronomer Sir Patrick Moore. Ross says his life has revolved around submarines since 1959 and he finds this new concept of a submarine on Europa to be very exciting.

McKinnon classifies the exploration of Europa as “extremely important.”

“Europa is a place is where we are pretty sure we have abundant liquid water, energy sources, and biogenic elements such as carbon, nitrogen, sulfur, phosphorus, etc,” he said. “Is there life, any kind of life, in Europa’s ocean? Questions don’t get much more profound.”

Written by Nancy Atkinson

Did Life on Earth Originate With Comets?

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The traditional thinking is that life on Earth began… on Earth. At some point in our distant past, some mixture of amino acids made the jump from a pool of organic molecules to something more lifelike. But maybe the source of life on Earth came from space, hitching a ride aboard balls of ice and dust: comets.

This is the controversial theory proposed by Chandra Wickramasinghe, an astrobiologist at Cardiff University in the United Kingdom. Wickramasinghe is one of the long time proponents for the theory of panspermia; that life on Earth originated from space or another planet.

Wickramasinghe and his team are claiming that new evidence gathered by space probes reveals how these first organisms could have gotten started.

When NASA’s Deep Impact spacecraft ended its life in 2005, crashing into Comet Tempel 1, it discovered a mixture of organic and clay particles inside the comet. One theory about the origins of life is that clay particles act as a catalyst, allowing simple organic molecules to get arranged into more and more complex structures. The 2004 Stardust mission found a range of complex hydrocarbon molecules when it collected particles from Comet Wild 2.

The Cardiff team think that radioactive elements inside comets could make pockets warm and toasty enough to keep water in its liquid form for millions of years. These iceballs could serve as the perfect incubators for early life. And when one finally crashes into a planet, it delivers this life to its new home.

There are so many comets out there, with potentially so many liquid pockets inside, that Wickramasinghe and team calculated that the likelihood is far greater that life got started in comets, and not here on Earth.

With any controversial theory, there are many scientists who think this is just too speculative. Without actual evidence for one of these oases inside a comet, it’s just an interesting idea. Perhaps ESA’s Rosetta mission, currently on its way to Comet 67P/Churyumov-Gerasimenko, and equipped with a lander will be just to tool to gather this kind of evidence.

Original Source: Cardiff News Release

Self Organizing Space Dust Could Be a Precursor to Life

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As if searching for life wasn’t already difficult enough, physicists now think that clouds of particles in space could mimic the behaviour of life: dividing, replicating and even evolving. This discovery could help scientists understand how life got started here on Earth, and offers intriguing possibilities for life that could evolve in the interstellar clouds of outer space.

This discovery comes from European and Australian researchers, and their work is published in today’s issue of the New Journal of Physics. They developed computer simulations that showed how clouds of molecules naturally organize themselves into complex helix-like structures that resemble DNA.

Over time, an electrical process called polarization organizes the molecules into more and more complex structures. According to the researchers, this suggests a mechanism where organic molecules could assemble faster than in previous models. This shorter time frame means that complex life could be prevalent across the Universe – they get part of the way in space, and then finish off when they reach a planet. Astronomers have already observed vast clouds of these particles out in space with radio telescopes.

Life on Earth requires water, and these molecules wouldn’t have access to the liquid in the near absolute zero temperatures of interstellar space; however, they are able to interact through this polarization process. So there might be a limit, where the structures can’t become complex enough to seed life on young planets. But this process could begin the formation of life, from a random collection of atoms to more complex molecules, and eventually the precursors of life. Evolution could then take over.

Original Source: Science Now

Enceladus is an Unlikely Home for Life

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When Cassini discovered geysers of water ice fountaining off of Saturn’s moon Enceladus, it was easy to think: life! Wherever we have liquid water here on Earth, scientists have found microbial life thriving; even in the strangest environments. A new model of just how Enceladus generates those geysers has made the possibility of microbial life being able to survive on Enceladus very unlikely.

When the geysers were first discovered, scientists dubbed the process “Cold Faithful”. In this model, tidal interactions between Enceladus and Saturn heat the moon, creating shallow pockets of liquid water under an ice shell. Pressure builds up under the ice, causing it to burst open, and water ice to spray out into space.

But a new model, developed by researchers at the University of Illinois, explains how Enceladus could be producing geyser-like plumes of water ice without an environment hospitable to life. Instead, the process would be called “Frigid Faithful”, and wouldn’t require liquid water at all.

Enceladus is covered in a layer of stiff ice compounds called clathrates, which could go down to a depth of tens of kilometres. Even with a moderately warm heat source underneath the moon’s south pole, these clathrates could deform and create the tiger stripe cracks and fractures which have been observed.

Instead of having pools of water near the surface, these cracks extend down up to 35 kilometres, and maintain almost the exact same temperature all the way down – as cold as 150 degrees below zero. And that wouldn’t be hospitable to life.

So where are the geysers coming from? As the clathrates dissociate, they produce gases that travel up the tiger stripes. This gas then leaks into space, and seen as the plumes that Cassini observed. Here’s what one of the researchers, Gustavo Gioia, had to say:

“This is indeed a frigid Enceladus. It appears that high heat fluxes, geyser-like activity and complex tectonic features can occur even if moons do not have hot, liquid or shifting interiors.”

Original Source: UIUC News Release

An Experiment to Test Panspermia

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One of most intriguing, and controversial, theories astrobiology is the concept of Panspermia. This idea proposes that life on Earth might have began on another planet, or maybe even out in interstellar space. Scientists have discovered just how hardy microbial life can be, surviving long journeys in the vacuum, cold, and radiation of space. Now an experiment has been devised to see how well microbes can withstand reentry through the Earth’s atmosphere.

The experiment, designed by Professor John Parnell from the University of Aberdeen, involves bolting a Scottish rock to the outside of an ESA research spacecraft. When the Foton M3 mission launches on Friday, September 14th, microbes in the rock will enjoy the acceleration of liftoff, 12 days of microgravity and vacuum, and then re-entry through the Earth’s atmosphere.

“The objective behind this is to look at the rock’s behaviour when it is exposed during re-entry through the Earth’s atmosphere – when temperatures are extreme. This will tell us something about the likelihood of life being transferred between planets on meteorites.

“The Orkney rock is a very robust material but it will be interesting to see if organic matter in the rock is robust enough to survive the harsh conditions endured during re-entering the Earth’s atmosphere.”

In theory, asteroid strikes in the past excavated material on other planets, hurling microbe-laden rocks into interplanetary space. The rocks would then act as lifeboats, carrying the microbes to other planets. More importantly, they should protect the bacteria as the rock plunges into the atmosphere.

This experiment will help discover if there’s anything to this idea. Bacteria might just be hardy enough to survive the complete journey from planet to planet.

Original Source:Univ. Of Aberdeen