- Joined
- Aug 7, 2001
- Messages
- 54,631
I don't suppose we'll hear much more about stardust now until it reaches the comet.The encounter images show Annefrank to be irregularly shaped, cratered, and about 8 kilometers (5 miles) in diameter. Stardust's dust instruments were on for the encounter, although no dust was anticipated. Scientists are still checking data to see if, by chance, the instruments may have seen a dust particle. "The dust flux measurement instrument ran for at least 27 minutes and performed all expected functions," said Dr. Tom Economou of the University of Chicago, lead scientist for that instrument. The lead scientist for Stardust's interstellar dust analyzer, Dr. Jochen Kissel of Max Planck Institute, Garching, Germany, said the Annefrank experience will enable him to put the German instrument into an even better configuration at Wild 2.
Full story: http://www.space.com/searchforlife/seti_devore_leonids_021114.htmlThe team is planning to observe two meteor storms predicted for the night of November 18-19. Astronomers expect the Earth to plunge through the remains of two dust trails shed by Comet Tempel-Tuttle. First, they'll encounter dust shed in 1767 (visible from Europe), and then the 1866 trail (visible from the Americas) more than 6 hours later. There's even an experiment with sticky tape where researchers hope to pick up particles from the meteor shower that filter down to aircraft altitudes.
So spores and even desiccated cells survive space and sunlight. But can they survive long enough to travel between, say, Mars and Earth?
The LDEF mission showed spores surviving six years, and six years is a realistic time frame for travel between Earth and Mars, the other planet in our solar system most likely to harbor life, Mancinelli and Horneck agree. But for longer trips, all scientists can do is calculate.
"If the time becomes too long, then the cosmic radiation that penetrates the rock would finally be lethal," Horneck says. "We have calculated (in the Mileikowsky paper in Icarus (2000) that in order to protect spores for 1 million years against cosmic radiation, a 1-meter-thick layer of the meteorite is necessary."
So spores and even desiccated cells survive space and sunlight. But can they survive long enough to travel between, say, Mars and Earth?
The LDEF mission showed spores surviving six years, and six years is a realistic time frame for travel between Earth and Mars, the other planet in our solar system most likely to harbor life, Mancinelli and Horneck agree. But for longer trips, all scientists can do is calculate.
"If the time becomes too long, then the cosmic radiation that penetrates the rock would finally be lethal," Horneck says. "We have calculated (in the Mileikowsky paper in Icarus (2000) that in order to protect spores for 1 million years against cosmic radiation, a 1-meter-thick layer of the meteorite is necessary."
Extra terrestrial microorganisms present in atmosphere: Indo-British study
16.38 IST 30th Nov 2002
By IndiaExpress Bureau
A study conducted by a joint Indo-British team of scientists has confirmed the presence of extra-terrestrial microorganisms, entering via earth’s atmosphere.
The team employing the Indian Space Research Organization’s cryogenic sampler balloon payload, to test the presence of these microorganisms found them in the earth’s stratosphere at a height of 41 km. The samples collected have been extensively analyzed by scientists both India and the United Kingdom.
The results, interalia suggestive of the presence and entry of extra-terrestrial microorganisms into the earth’s atmosphere, were presented at several international symposia, conferences in the United States, Europe as well as in India. The experiment and the results were well received. After exhaustive international scientific scrutiny, a paper containing the path-breaking findings have been accepted by the journal "Microbiology letters" of the Federation of European Microbiology Societies. Further study of these microorganisms are underway.
Interesting idea, but it ain't necessarily so (as the song says). It seems that extreme events like meteor strikes or major vulcanism may be needed to get stuff out of Earth's gravitational well, so it may be that most of the surrounding stuff is actually inbound (or just passing by).Eburacum45 said:..but it seems obvious that if you go to within 50 km of the earth, 99.999% of the organisms collected will be earthly in origin
there might even be a whole ecology of extremophiles up there
a mirror of the subterranean ecology deep underground
Meteorite yields early organic material
From staff reports
The Daily News
Published December 16, 2002
CLEAR LAKE — Researchers said a meteorite that fell to Earth over northwestern Canada in 2000 contains a previously unseen type of primitive organic material that was formed long before our own solar system came into being.
The finding was published last week in the International Journal of Astrobiology. The Tagish Lake meteorite fell to Earth over the Yukon Territory on Jan. 18, 2000.
Parts of the meteorite were collected and kept frozen in an unprecedented level of cleanliness to ensure that it was not contaminated by any terrestrial sources. The researchers found numerous hollow, bubble-like hydrocarbon globules in the meteorite.
They believe these organic globules, the first found in any natural sample, are very similar to those produced in laboratory simulations designed to recreate the initial conditions present when life first formed in the universe.
“While not of biological origin themselves, these globules would have served very well to protect and nurture primitive organisms on Earth,” said Michael Zolensky, an author of the paper and a researcher in the Office of Astromaterials Research and Exploration Science at NASA’s Johnson Space Center. “They would have been ready-made homes for early life forms.”
The type of meteorite in which the globules were found is so fragile that it generally breaks up into dust during its entry into Earth’s atmosphere, scattering its organic contents across a wide swath.
“If, as we suspect, this type of meteorite has been falling onto Earth throughout its entire history, then the Earth was provided with these hydrocarbon globules at the same time life was first forming here,” Zolensky said. “We were exceedingly fortunate that this particular meteorite was so large that some pieces survived to be recovered on the ground.”
There must be thousands of Martian meteorites on Earth, and the notion of "seed-bearing meteoritic stones" was raised by Lord Kelvin in 1871, and the notion of free spores drifting through space and seeding life on other planets ( "panspermia") was postulated by the Swedish chemist Arrhenius a few years later (an idea revived in the twentieth century by Francis Crick and Fred Hoyle). The idea was considered implausible for more than a century, but is once again a hot subject for discussion. For now, it is evident that the insides of sizeable meteors do not get heated to sterilizing temperatures, and that bacterial spores, or other resistant forms, could, in principle, survive within them, protected by the body of the meteor not only from heat but from radiations deadly to life. Meteors were being flung in all directions during the period of Heavy Bombardment four million years ago. Chunks of the Earth must have been ejected into space then, as well as chunks of Mars and Venus - a Mars and Venus which might, at the time, have been more hospitable to life than Earth itself.
But we may not need to look too far afield for such meteors. We already know, from the samples returned by the Apollo missions, that there are early Earth and Martian meteors on the moon in considerable quantities. Now, perhaps, the time has come to plan a new mission to the moon, to allow mining and soil-concentration experiments that utilize technology unimaginable in the 1970s (such as portable polymerase machines to search the soil for ancient DNA). Here, perhaps, more easily than anywhere else, we may hope to find traces of the earliest life forms from Earth, or Venus, or Mars, and determine how life first started in our solar system.
Meteorite yields early organic material
Its organic but not biological? Does that mean that it comes from terrainia but is not the product of life? I genuinely did not know that there was a difference. Is that the difference then?primitive organic material.....organic globules........While not of biological origin themselves
Not sure what you mean by the Moon being placed perfect - according to the latest thinking, the moon itself is the end result of a massive inpact on the Earth during the bombardment era. Also, it is slowly moving away from the Earth under tidal interactions - does that mean it's getting less perfect?ruffready said:Its perfect, our moon "placed" perfect. all the gas giants way out there doing their blocking action thing
Hic! :madeyes:Astronomers already know that there are 10 billion, billion, billion litres of methanol and ethanol in the Sagittarius B2 cloud.
GuardianIs our planet really being bombarded with life from outer space?
Ian Sample
Thursday May 29, 2003
The Guardian
It most certainly is, says Chandra Wickramasinghe at the Cardiff Centre for Astrobiology. It most certainly isn't, say the overwhelming majority of other scientists.
In the 1970s, Wickramasinghe and the late astronomer Fred Hoyle proposed the theory that life was originally brought to the barren Earth by comets. The comets, they said, shed organic molecules and alien microbes as they passed by the Earth and some of those became established once they hit the ground. Last week, Wickramasinghe wrote in the Lancet that the Sars virus, still causing havoc in south east Asia, might have dropped to Earth in such a way.
Not likely, says William Grant at the University of Leicester who studies microbes in extreme environments. The very act of tolerating space would make alien microbes, should there be any nearby, hopeless human pathogens. Suppose a clump of alien microbes were hurtling through space on a comet. The bacteria would only survive if evolution resulted in their adapting to the intensely cold, radiation-rich vacuum of space. The process itself might take millions of years. If they did survive, they would be so well adapted to living in space, they could never thrive on Earth, let alone have the necessary molecular machinery to invade human cells and cause disease, says Grant.
On Earth, new human viruses tend first to linger in animals with at least similar physiology to humans. Then, as the virus evolves to dodge the animal's immune system, a chance mutation might just make it capable of jumping species into a human. That evolutionary process would not take place if the virus was flying through space on a lump of rock.
"In the case of Sars, the virus needs a specific protein to bind to human cells and enable it to enter them. It's extremely complicated. The idea that it could just have evolved without being in a very similar environment, an animal, is nonsense," says Ian Jones, a virologist at the University of Reading. "The evolutionary pressure would never be there for the protein to form."
Scientists have long known that complex molecules can form in space, and meteorites discovered on Earth have been found to contain amino acids, the building blocks of proteins. But these are a far cry from living organisms, says Jack Cohen, a biologist at the University of Warwick and part-time 'alien creature designer' for science fiction writers. "Some scientists think that if you can get complex molecules, some of them might be diseases. They don't understand how complicated something has to be before it can be an effective disease," he says.
Wickramasinghe says his critics reject his theory because they are convinced life originated on Earth. If life came from elsewhere, then organisms on different planets would evolve together, he says, making the chance of alien microbes able to infect humans more likely. "The only way it works is that evolution is not restricted to Earth, but happens on a huge cosmic scale. Life on Earth is connected with life everywhere in the universe," he says.
The worst aerial bombardment in the history of the world started 3.8 billion years ago, when asteroids began slamming into the planet every 20 years or so. Some were the size of Manhattan, others as large as North America. Each hit with the force of all of the nuclear devices on Earth exploding at once. They spewed up gas and debris, blocking sunlight and creating gigantic craters.
For years, many scientists have focused on the destructive role asteroids have played in the history of life on Earth, possibly wiping out the dinosaurs 65 million years ago and contributing to, if not causing, the mass extinctions found in the fossil record every 26 million to 30 million years or so. Astronomers monitor the heavens, searching for menacing hunks of space rock that may be heading our way.
There is, however, a positive side to asteroids, and one that a handful of researchers has been investigating with renewed vigour in recent years. True, an incoming asteroid the size of Manhattan could be a civilization ender, killing all humans and many other species. But what if asteroids were the source of life on Earth in the first place?
David Kring thinks that is a possibility. A planetary scientist at the University of Arizona, he says the timing is right.
The first traces of life on Earth, found in rocks from Greenland, date to 3.8 million years ago, around the time of the great bombardment. Back then, Earth was a flooded planet, covered by a single shallow sea and lit by the dim fire of a young sun.
It is hard to imagine even one asteroid slamming into our planet, let alone one crashing every 20 to 200 years. To get a sense of the damage, look up at the moon on a clear night. Those ancient pockmarks were made in the same rocky barrage, Dr. Kring says.
Unlike the dusty lunar craters, those on Earth soon bubbled with hot water like primordial Jacuzzis. Their heat source was the molten and shattered rock at the bottom of the crater that absorbed much of the energy of the initial impact. Those rocks were hot enough to heat the water for hundreds of thousands of years. Voilà, Dr. Kring says, a cauldron for the soup of life.
As for the soup ingredients, all the elements needed for life were on board asteroids, which contain hydrogen, oxygen, sulphur, nitrogen and phosphorus. As many as 700 amino acids, the building blocks of proteins, have been detected on space rocks that have landed on Earth.
The general theory about the evolution of life is that these kinds of compounds --whether they came from asteroids or were already here -- eventually gave rise to a single-celled organism such as a bacterium. Exactly how that happened is still a mystery.
Dr. Kring was the first to put forward the idea that asteroid craters were the hydrothermal brew pits for early life. It is a hard theory to prove, however. None of the craters that were formed 3.8 billion years ago remain. They were erased by shifting continents and mountain building. That means Dr. Kring and his colleagues have to glean what they can from the 171 more recent impact sites that have been found on Earth, including 31 in Canada.
The idea of impact sites as "cauldrons of life" has been embraced by scientists investigating the possibility of life on Mars. The red planet is home to many impact craters, and was bombarded with asteroids 3.8 billion years ago when Earth and the moon were regularly hit.
Gordon Osinkski, a researcher at the University of New Brunswick, is part of a team of investigators who have spent the last five summers studying an impact crater on Devon Island in Nunavut. The Haughton Crater is 20 kilometres in diameter, and looks much like the surface of Mars today. But the area would have been much wetter and warmer when an asteroid or comet hit 23 million years ago.
Mr. Osinkski found pipe-like structures around the crater rim, and believes that they acted as vent systems for hot fluid and steam, bringing warm water and chemicals to the surface. "It seems very likely you would have hot springs around the Haughton Crater."
If the same structures are found in Martian craters, it would build the case that life may have evolved there as well. Images from the surface of Mars suggest that water once flowed on its surface.
"Hydrothermal systems represent sites where water, warmth, dissolved chemicals and nutrients may have been available for extended lengths of time. Haughton may therefore provide a valuable case study for understanding how impact-generated hydrothermal systems affected the development of life on early Earth, and possibly other planets such as Mars,'' Mr. Osinkski says.
Others are convinced that life evolved first elsewhere in the universe. In the 1970s, British astronomers Fred Hoyle and Chandra Wickramasinghe argued that bacteria can travel across galaxies on comets. According to their theory, life arrived on Earth riding on a celestial snowball.
While asteroids are composed of metal and rock, comets are made of ice. There is no definitive proof that comets -- or asteroids -- ever arrived on Earth carrying bacteria. But a few weeks ago, in the prestigious U.S. journal Science, Belgian researchers announced new evidence that comets carry large quantities of complex organic compounds. These are the kinds of compounds that could give rise to life.
The problem with comets, in more ways than one, is that they tend to travel faster than asteroids, and so slam into Earth with a greater destructive force. There is still debate over whether the impact crater in Mexico associated with the death of the dinosaurs was caused by a comet or an asteroid.
In any event, the question is whether any living organism -- or the raw chemical material for life -- could survive that kind of cataclysm.
Dr. Kring doesn't think so. But there is evidence they could survive the relatively milder cataclysm of an asteroid impact, says Gordon Southam, a researcher at the University of Western Ontario. He and his American colleague Eileen Ryan tried to simulate the force of an asteroid hitting Earth on a small scale, using small chunks of rock inhabited by bacteria.
"We fire projectiles at two kilometres a second at a rock and basically blow it up," he says. Their results have not yet been published, but he says the bacteria survive.
Surviving the initial impact is one challenge. Temperatures in the "cauldron" formed by the crater would probably have been too high for even heat-loving bacteria to withstand, and might have burned off any carbon or other building blocks of life.
Which brings us to the alternative hydrothermal theory of life. Impact craters may not have been the only hydrothermal environments on Earth 3.8 billion years ago. There were hydrothermal vents at the bottom of the ocean, cracks in the sea floor that are still there today, although the oceans are now much deeper. Hot gas bubbles up through the cracks, along with nitrogen, hydrogen, carbon, methane and sulphate -- the basic ingredients for amino acids.
Kim Juniper is a University of Quebec professor who spends his summers studying the strange creatures that live around the vents, including string-like tube worms, giant clams and spiders, as well as heat-resistant bacteria.
He believes it is more likely that life evolved first in the vents. Dr. Kring agrees that this is a possibility, and says it is impossible to know for sure. There is also a chance that life evolved earlier than 3.8 billion years ago, but was extinguished when the worst asteroid storm in history began. Researchers believe each impact would have been a natural disaster unprecedented in modern times, turning the surface of Earth into a convection oven, and raised enough dust to block out the rays of the sun for years.
"One of the things we still don't understand is whether the bombardment created the conditions necessary for the origin of life, or extinguished pre-existing life forms," Dr. Kring says.
However, both scenarios suggest that humans may owe their existence to heavenly bodies. If asteroids and comets did give rise to life, then we would not have evolved without them.
Some scientists look at asteroid impacts as periodically purging the world of many of its animals, allowing only small, hardy generalists to survive. This regular cleansing, while disastrous for the species that die, regularly clears the decks for the rise of a new world order.
The last major impact was 65 million years ago, when either a comet or an asteroid 10 to 15 kilometres in diameter smashed into the Yucatan Peninsula in Mexico. It may have killed off the dinosaurs and ended the age of the reptile. But it also gave rise to the age of the mammal, which eventually produced Homo sapiens.
Space radiation may select amino acids for life
11:24 24 August 2005
NewScientist.com news service
Maggie McKee
Space radiation preferentially destroys specific forms of amino acids, the most realistic laboratory simulation to date has found. The work suggests the molecular building blocks that form the "left-handed" proteins used by life on Earth took shape in space, bolstering the case that they could have seeded life on other planets.
Amino acids are molecules that come in mirror-image right- and left-handed forms. But all the naturally occurring proteins in organisms on Earth use the left-handed forms - a puzzle dubbed the "chirality problem".
"A key question is when this chirality came into play," says Uwe Meierhenrich, a chemist at the University of Nice-Sophia Antipolis in France. One theory is that proteins made of both types of amino acids existed on the early Earth but "somehow only the proteins of left-handed amino acids survived", says Meierhenrich.
Meierhenrich and colleagues have a different theory. "We say the molecular building blocks of life were already created in interstellar conditions," he told New Scientist.
The team believes a special type of "handed" space radiation destroyed more right-handed amino acids on the icy dust from which the solar system formed. This dust, along with the comets it condensed into, then crashed into Earth and other planets, providing them with an overabundance of left-handed amino acids that went on to form proteins.
Magnetic alignment
The radiation is called circularly polarised light because its electric field travels through space like a turning screw, and comes in right- and left-handed forms.
It is thought to be produced when dust grains become aligned in the presence of magnetic fields threading through regions of space much larger than our solar system. Circularly polarised light is estimated to make up as much as 17% of the radiation at any given point in space.
In 2000, an experiment showed that when circularly polarised ultraviolet light of a particular handedness was shone on an equal mix of right- and left-handed amino acids, it produced an excess of 2.5% by preferentially disintegrating one type.
But that experiment was done using amino acids in a liquid solution, which behave differently than those in the solid conditions of icy dust in space. To avoid absorption by water molecules, it was also necessary to use light at a wavelength of 210 nanometres – significantly longer than the peak of 120 nm radiation actually measured in space.
Biased meteorites
Now, Meierhenrich's team has performed a similar experiment. The group shone circularly polarised light at a wavelength of 180 nm on a solid film of both right- and left-handed forms of the amino acid leucine. It found that left-handed light produced an excess of 2.6% left-handed amino acids.
"Going towards greater realism by exploring another wavelength of light and solid samples is definitely a good thing and a logical step forward," says chemist Max Bernstein of NASA's Ames Research Center in California, US, who is not part of the team.
He says the research adds to previous measurements of an excess of left-handed amino acids in two meteorites. "If it is thanks to meteorites that our amino acids are left handed, then the same bias should exist at least across our solar system", he told New Scientist.
Alien life
But other solar systems may harbour right-handed amino acids if they are subjected to the other type of circularly polarised light, says Meierhenrich.
"The chiral amino acids might have been delivered to other planets, to other solar systems," he adds. "The probability that life arose somewhere else is increased with this experimental result."
Meierhenrich will continue to reduce the wavelength of the experimental radiation by using a synchrotron facility, due to begin operating in 2006. But the real test of his theory may come in 2014, when the European Space Agency's Rosetta spacecraft lands a probe on Comet 67P/Churyumov-Gerasimenko.
He designed an instrument for the lander that will measure the handedness of any amino acids it finds. "If we identify left-handed amino acids on the cometary surface, this would underline the hypothesis that the building blocks of proteins were created in interstellar space and were delivered via comets or micrometeorites to early Earth," he says.
http://www.newscientistspace.com/article.ns?id=dn7895