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Artist of Life
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Life Out There?
Water: The first, and most obvious, indication of life outside of Earth is water. You would be hard pressed to find a creature that isn't dependent on some form of water, whether it be microscopic, or twelve feet tall. The most debated instances where microbic life may strive is Jupiter's moon, Europa. Covered by a thin layer of ice, this moon is theorized to have a molten core due to its faint lingering magnetic field. Where the two layers meet is where it is possible for life to exist, a possible ocean. Aside from these instances, scientists have also found amino acids and nutrients on asteroids.
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Diane Ainsworth
FOR IMMEDIATE RELEASE July 22, 1999
SUN NEVER SETS, FOR LONG, ON FAST-SPINNING, WATER-RICH ASTEROID
Spinning faster than any object ever observed in the solar system, a lumpy, water-rich sphere known as 1998 KY26, about the diameter of a baseball diamond, is rotating so swiftly that its day ends almost as soon as it begins, NASA scientists report.
Asteroid 1998 KY26, where the Sun rises or sets every five minutes, was observed June 2-8, 1998, shortly after it was discovered and as it passed 800,000 kilometers (half a million miles) from Earth, or about twice the distance between Earth and the moon. Publishing their findings in tomorrow's issue of Science magazine, Dr. Steven J. Ostro of NASA’s Jet Propulsion Laboratory, Pasadena, CA, and an international team of astronomers used a radar telescope in California and optical telescopes in the Czech Republic, Hawaii, Arizona and California to image the 30-meter (100-foot), water-rich ball as it twirled through space. It is the smallest solar system object ever studied in detail.
"These observations are a breakthrough for asteroid science and a milestone in our exploration of the small bodies of the solar system," Ostro said. "Enormous numbers of objects this small are thought to exist very close to Earth, but this is the first time we've been able to study one in detail. Ironically, this asteroid is smaller than the radar instruments we used to observe it."
The asteroid's rotation period was calculated at just 10.7 minutes, compared to 24 hours for Earth and at least several hours for the approximately 1,000 asteroids measured to date. In addition to these findings, the minerals in 1998 KY26 probably contain about a million gallons of water, enough to fill two or three olympic-sized swimming pools, Ostro said.
"This asteroid is quite literally an oasis for future space explorers," he said. "Its optical and radar properties suggest a composition like carbonaceous chondrite meteorites, which contain complex organic compounds that have been shown to have nutrient value. These could be used as soil to grow food for future human outposts. And among the 25,000 or so asteroids with very reliably known orbits, 1998 KY26 is in an orbit that makes it the most accessible to a spacecraft."
The solar system is thought to contain about 10 million asteroids this small in orbits that cross Earth's, and about 1 billion in the main asteroid belt between Mars and Jupiter. However, only a few dozen of these tiny asteroids have ever been found and, until now, hardly anything was known about the nature of these objects.
Ostro and his colleagues used the 70-meter-diameter (230- foot) Goldstone, CA, antenna of NASA's Deep Space Network to transmit radar signals continuously to the asteroid and turned a 34-meter-diameter (112-foot) antenna on it to collect echoes bouncing back from the object.
1998 KY26's color and radar reflectivity showed similarities to carbonaceous chondrites, primordial meteorites which formed during the origin of the solar system, and unlike any rocks formed on Earth. They contain complex organic compounds as well as 10 percent to 20 percent water. Some carbonaceous chondrites contain amino acids and nucleic acids, which are the building blocks of proteins and DNA, and hence, are of interest to scientists trying to unravel the origins of life.
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Thermal Vents:
Life around thermal vents is a recent discovery (about 20 years) that has changed our idea of what a suitable environment for life can be. The following is an article written by one of Popular Science magazine's editors on the Alvin expedition investigating thermal vents off the coast of the Galapagos.
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Creatures of the Thermal Vents
by Dawn Stover
The three-person submersible Alvin sank through the cold, dark waters of the Pacific Ocean for more than an hour, finally touching down on the sea floor more than 8,000 feet below the surface. It was December 1993, and the scientists inside the sub had come to this stretch of the East Pacific Rise, an underwater mountain range about 500 miles southwest of Acapulco, Mexico, to inspect a recently formed hydrothermal vent - a fissure in the ocean bottom that leaks scalding, acidic water.
Peering out through the sub's tiny windows, the visitors were astonished to see thickets of giant tube worms, some four feet tall. The tail ends of the worms were firmly planted on the ocean floor, while red plumes on the other ends swayed like a field of poppies. Alvin had brought researchers to the same spot less than two years earlier, when they had seen none of these strange creatures. Measurements at the site have since shown that individual tube worms can increase in length at a rate of more than 33 inches per year, making them the fastest-growing marine invertebrates. That means tube worms can colonize a vent more rapidly than scientists once thought.
The giant tube worm is one of the most conspicuous members of a diverse community that forms around hydrothermal vents. Scientists once thought that no living thing could survive the harsh combination of toxic chemicals, high temperatures, high pressures, and total darkness at these vents. But in 1977, researchers diving in Alvin discovered tube worms and other bizarre organisms thriving at a vent off the Galapagos Islands. Similar communities have since been found at several hundred hot spots around the world. These creatures are like nothing else on Earth.
Vents form where the planet's crustal plates are slowly spreading apart and magma is welling up from below to form mountain ranges known as mid-ocean ridges. As cracks form at these spreading centers, seawater seeps a mile or two down into the hot rock. Enriched with minerals leached from the rock, the water heats and rises to the ocean floor to form a vent.
Vents are usually clustered in fields, underwater versions of Yellowstone's geyser basins. Individual vent openings typically range from less than a half inch to more than six feet in diameter. Such fields are normally found at a depth of more than a mile. Most have been discovered along the crest of the Mid-Oceanic Ridge, a 46,000- mile-long chain of mountains that wraps around Earth like the seams on a baseball. A few vents have also been found at seamounts, underwater volcanoes that are not located at the intersection of crustal plates.
The largest vent field, called TAG (short for Trans-Atlantic Geotraverse), is about the size and shape of a football stadium. Other fields have more whimsical names like Clam Acres, Mussel Bed, Rose Garden, Garden of Eden, Broken Spur, and Lucky Strike. Snow Blower is named for the white, flaky bacteria discharged from its vents. Genesis is a vent that sputtered out but came back to life a few years later.
Hydrothermal vents are underwater oases, providing habitat for many creatures that are not found anywhere else in the ocean. More than 300 new species have been identified since the first vent was discovered in 1977.
Besides the giant tube worms, which have so far been found only in the Pacific, there are pencil-size Jericho worms with accordion-like tubes; orange worms covered with tiny bristles; small benthic worms that wriggle through the mud; and finger-length, dark red palm worms that stand upright, topped with wiglike fronds. A special class of small worms, called Alvinellids (named after the sub), live on the walls of mineral deposits that form around vents.
Mussels, shrimp, clams, and crabs are abundant at many vents, but these are not the same species that you find in seafood dishes. The cocktail-size shrimp that dominate vents in the mid-Atlantic, for example, have no eyes. However, at least one species has an extremely sensitive receptor on its head that may be used to detect heat or even dim light coming from vents. Scientists still aren't sure how shrimp and other vent creatures cope with chemical-laden seawater that would kill ordinary shellfish.
Biologists have observed a variety of smaller crustaceans around vents, including miniature lobsters called galatheids, and amphipods resembling sand fleas. They have also seen snail-like limpets the size of BBs, sea anemones, snakelike fish with bulging eyes, and even octopuses.
While octopuses are at the upper end of the vent's food chain, bacteria are at the bottom. They are the first organisms to colonize newly formed vents, arriving in a snowlike flurry and then settling to form white mats or tendrils attached to the ocean floor. Bacteria have been found living beneath the ocean's floor, and it seems likely that they emerge from below when the conditions are right. Vent bacteria can withstand higher temperatures than any other organism. That makes them attractive to researchers who are developing heat-stable enzymes for genetic engineering, and culturing bacteria designed to break down toxic waste.
Water pouring out of vents can reach temperatures up to about 400 C; the high pressure keeps the water from boiling. However, the intense heat is limited to a small area. Within less than an inch of the vent opening, the water temperature drops to 2 C, the ambient temperature of deep seawater. Most of the creatures that congregate around vents live at temperatures just above freezing. Thus chemicals are the key to vent life, not heat.
The most prevalent chemical dissolved in vent water is hydrogen sulfide, which smells like rotten eggs. This chemical is produced when seawater reacts with sulfate in the rocks below the ocean floor. Vent bacteria use hydrogen sulfide as their energy source instead of sunlight. The bacteria in turn sustain larger organisms in the vent community.
The clams, mussels, tube worms, and other creatures at the vent have a symbiotic relationship with bacteria. The giant tube worms, for example, have no digestive system - no mouth or gut. "The worm depends virtually solely on the bacteria for its nutrition," says microbial ecologist Colleen M. Cavanaugh of Harvard University. "Both partners benefit."
The brown, spongy tissue filling the inside of a tube worm is packed with bacteria - about 285 billion bacteria per ounce of tissue. "It's essentially a bacterial culture," says Cavanaugh.
The plumes at the top of the worm's body are red because they are filled with blood, which contains hemoglobin that binds hydrogen sulfide and transports it to the bacteria housed inside the worm. In return, the bacteria oxidize the hydrogen sulfide and convert carbon dioxide into carbon compounds that nourish the worm.
Tube worms reproduce by spawning: They release sperm and eggs, which combine in the water to create a new worm. Biologists don't know how the infant worm acquires its own bacteria. Perhaps the egg comes with a starter set.
Scientists also don't know how tube worms and other organisms locate new vents for colonization. "The vents are small, and they're separated, like islands," says Cindy Lee Van Dover, a biologist and Alvin pilot who studies vent life. Most vent organisms have a free- swimming larval stage. But scientists aren't sure whether the larvae float aimlessly or purposely follow clues - such as chemical traces in the water - to find new homes.
Studying the life cycle of vent organisms is difficult. Researchers have visited only a fraction of the ocean's hot spots. They have been able to observe vent life only by shining bright lights on creatures accustomed to inky darkness, and many specimens die quickly when removed from their unique environment. Underwater cameras are helping scientists make less intrusive observations, but diving expeditions are still the most useful way to gather information. The 1993 Alvin expedition to the East Pacific Rise was one in a series of dives to the area. The site was first visited in 1989, and scientists observed vent organisms thriving there. But when Alvin returned in April 1991, its flabbergasted occupants witnessed the birth of a hydrothermal vent. A recent volcanic eruption had spread glassy lava across the ocean floor, and the researchers measured temperatures up to 403 C - the hottest ever recorded at a hydrothermal vent. The scientists dubbed the site Tube Worm Barbecue, because the worms they brought back to their ship had charred flesh.
"The most spectacular sight down there was this massive blinding snowstorm of bacteria," says Rich Lutz, a marine ecologist at Rutgers University, who led the expedition. On the ocean floor, the bacteria formed mats several inches thick, but the scientists saw no other living things.
Since the eruption, scientists have been able to watch several stages of colonization at the site. When they returned in March 1992, only a few bacterial mats remained. In their place were colonies of Jericho worms and a variety of small crustaceans. The scientists named the area Phoenix, because new life had arisen from the ashes of the eruption.
The scientists first observed the giant tube worms at Phoenix in December 1993. They also noticed a number of mineral deposits, some towering to heights of more than 30 feet. These structures form where hot vent water meets cold seawater, causing metal sulfides to precipitate out. The precipitating sulfides, which look like smoke, amass to form chimneys called black smokers. Like the vent fields, some smokers have names. Smoke and Mirrors, for example, has shelflike overhangs that trap hot water rising from below, creating upside-down shimmering pools. The largest known black smoker is Godzilla, a 160-foot-tall structure off the coast of Oregon.
During a December 1993 dive to the Phoenix vent field, Alvin accidentally toppled a 33-foot-tall smoker. When the sub returned for a brief visit three months later, the chimney had already grown back 20 feet. Scientists were surprised by the speedy recovery, which seems to parallel the rapid growth of tube worms and other organisms at the vents. The visits to the Phoenix site "give us a sense of how quickly these vents are colonized," says Van Dover.
Another expedition is planned for November. By then, the community of organisms now prospering at the vents may already be a ghost town. When the flow of hot, sulfide-rich water slows to a trickle, death also comes quickly.
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Hydrogen Sulfide:
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(Excerpt from Genentech Inc.'s national educational program for biology, 7/30/97)
Now bacteria, free living bacteria, in this environment and in our own backyard, have been known for years to be able to use chemical energy as a basis of their metabolism. So in the case of the free living bacteria, there are many sulfide oxidizing bacteria which can use chemical sulfide to basically run their metabolic pathways - to produce organic compounds, small nutrient compounds, that form the basis of their nutrition. What is happening in some of the hydrothermal vent animals is that they are harboring these chemical utilizing bacteria, within their body tissues. So for instance the large tubeworm, Riftia, and the clam, Caliptogena, harbored dense aggregations of bacteria, either in what was the residual gut of the tubeworm or in the gill area for the clam. These bacteria then are able to utilize the inorganic chemicals in the environment. They utilize hydrogen sulfide. What they do with the hydrogen sulfide is analogous to what plants do with photic energy. So it is called chemosynthesis rather than photosynthesis.
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Exobiology: Search for Evidence of Life: Considering the Improbable: Life Underground on Mars
By C.P. McKay, M. Ivanov, and P.J. Boston
The Viking results imply that there is no life on the surface of Mars. Conditions there are too cold, too dry and too oxidizing. This may be true, but beneath the surface things might be quite different.
The absence of liquid water, the result of low atmospheric pressure and low temperatures, makes the surface of Mars particularly inhospitable. Below the surface, with the weight of the overlying soil, obtaining pressures suitable for liquid water to exist would be no problem. Temperatures above freezing, however, would require a subsurface heat source: a smoldering volcano, or a magnetic hot spot.
Hot Evidence
Intriguing evidence for recent volcanic activity comes from a meteorite which fell in Shergotty, India (and other similar meteorites thought to have a common martian origin). The density of cosmic ray tracks in the meteorite’s lava crystals suggests that lava flowed on the surface of Mars about 200 million to 400 million years ago. The other martian meteorites are between 200 million and 1 billion years old. It is improbable that Mars was volcanically active for 4 billion years, only to become inactive in the last 200 million years. Nonetheless, it is important to keep in mind that no active volcanism has yet been observed on the Red Planet.
Volcanic activity itself does not provide a suitable habitat for life; liquid water, presumably derived from the melting of ground ice, is required. A volcanic source in the equatorial region probably would have depleted any initial reservoir of ground ice and there would be no mechanism for renewal, although there are indications of geologically recent volcano/ground ice interactions in this area. Closer to the poles, any ground ice would be stable. It is conceivable that a geothermal heat source here could bring about a cycling of water through the cryosphere. The heat source would melt ice and draw in water from any underlying reservoir of groundwater, brine or ice which might exist.
Moreover, the outflow channels on the martian surface appear to be the result of the catastrophic discharge of subsurface aquifers of enormous size. There is evidence based on craters and stratigraphic relationships that these floods have occurred throughout martian history, and intact aquifers may remain. Furthermore, the debris fields and outwash regions associated with the outflow channels may hold evidence of life which existed within the subsurface aquifer just prior to its catastrophic release.
Energy Without Light
The major disadvantage of living underground is that sunlight is not available for photosynthesis. Organisms would have to find another way to get the energy needed for life. There are examples of such light-less ecosystems on Earth. In deep-sea hydrothermal vents, the base of the food chain is the chemical oxidation of hydrogen sulfide (H2S) coming from the vent. Oxygen dissolved in the seawater is the oxidant.
This particular reaction would not work on Mars, because there is not enough oxygen in its atmosphere. However, there are other chemical schemes which microorganisms use that could be directly applicable to Mars with its carbon dioxide (CO2) atmosphere. For instance, a class of organisms known as methanogens can derive their life energy from the reaction of hydrogen (H2) and carbon dioxide to produce methane (CH4) and water (H2O).
Given a liquid water environment containing a source of hydrogen, these organisms could form the base of a food chain without light, without oxygen. The hydrogen would come from the volcanic activity below the surface. Thus, in addition to providing the heat to melt ice into liquid water, the geothermal source would also provide the basic chemical energy to support microbial life. Chemical schemes involving methane and hydrogen sulfide could work as well.
Life in (Imperfect) Isolation
Life could exist underground on Mars. But if it does, what are the implications for planetary protection?
First, consider that such subsurface ecosystems must be isolated from the surface. If they were not, they would not be able to maintain the salubrious conditions suitable for life but so dissimilar to the surface conditions. But they are unlikely to be completely closed either. There will inevitably be some leakage of material and organisms to the surface through vents and along cracks.
The isolated nature of these systems might make them resistant to contamination from terrestrial organisms deposited on the surface, so forward contamination by surface landers may not be an issue. However, from the point of view of back contamination, the situation is serious. If organisms living in subsurface niches develop spores capable of surviving, albeit in a dormant state, when exposed to the surface, then even small amounts of leakage from a geothermal habitat could spread these spores over the surface. Such spores would have been virtually undetectable by Viking, since the level of organic material implied was too low to be detected, and the Viking biology experiments were not equipped to search for them. It may be that the life of Mars’ underground will be a factor in future Mars missions.
C.P. McKay is a planetary scientist with NASA’s Ames Research Center.
M. Ivanov is a microbiologist and director of the Institute for Microbiology of the Russian Academy of Sciences.
P.J. Boston is a microbiologist with Complex Systems Research and a consultant to NASA.
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Methanogenic bacteria under Mar's surface?:
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BBC News Methane on Mars could signal life
By Dr David Whitehouse
Is there life beneath the soil?
Methane has been found in the Martian atmosphere which scientists say could be a sign that life exists today on Mars.
It was detected by telescopes on Earth and has recently been confirmed by instruments onboard the European Space Agency's orbiting Mars Express craft.
Methane lives for a short time in the Martian atmosphere so it must be being constantly replenished.
There are two possible sources: either active volcanoes, none of which have been found yet on Mars, or microbes.
Spectral signature
The spectral signature of the gas was seen by the Infrared Telescope on Hawaii and the Gemini South Observatory in Chile.
Scientists see two possibilities, both of them scientifically important, but one of them is sensational
Scientists operating the Mars Express Planetary Fourier Spectrometer (FPS) have announced they have detected the presence of methane in the Red Planet's atmosphere, too.
The world's largest telescope, the twin Keck facility on Hawaii, has looked but has yet to report its findings.
But further evidence of methane on Mars will be presented at a meeting next month by a consortium of astronomers using the Canada-France-Hawaii telescope.
Volcanic explanation
Methane is not a stable molecule in the Martian atmosphere. If it was not replenished in some way, it would only last a few hundred years before it vanished.
Scientists see two possibilities, both of them scientifically important, but one of them is sensational.
Nasa's Infrared Telescope detected methane last year
It is possible that the methane is being produced by volcanic activity. Lava deposited on to the surface, or released underground, could produce the gas.
This explanation has some difficulties, however. So far, no active volcanic hotspots have been detected on the planet by the many spacecraft currently in orbit.
If active volcanism were responsible then it would be a major discovery with important implications. The heat released by any volcanism would melt the vast quantities of sub-surface ice discovered on the planet, producing an environment suitable for life.
Life on Mars?
On Earth, there are organisms called methanogens - microbes that produce methane from hydrogen and carbon dioxide. These organisms do not need oxygen to thrive, and they are thought to be the type of microbes that could possibly live on Mars.
The twin US space agency rovers that landed on the Red Planet in January will be unable to answer the question of the methane's origin as they are designed for geological work.
But future missions could include sensors to analyse the methane to determine where it came from.
The failed Beagle 2 mission had a device that could have sniffed the Martian atmosphere for methane.
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So given the evidence at hand, what are your thoughts on life on other planets? Do you think our current findings are credible? Could some of these off-world life-forms be used to help terraform a planet? Could we help instigate the emergence of life on other planets? Let the debate begin.
Last edited by Ch'i; 09-12-2006 at 04:27 PM..
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09-12-2006, 04:21 PM
