Posted on by Fraser Cain

NASA and Department of Energy Working on Nuclear Reactor

Image credit: NASA/JPL
NASA has a new partner in its mission to explore the universe and search for life.

The Department of Energy’s (DOE) Naval Reactors (NR) Program joins NASA in its effort to investigate and develop space nuclear power and propulsion technologies for civilian applications. These activities could enable unprecedented space exploration missions and scientific return unachievable with current technology.

NR brings 50-plus years of practical experience in developing safe, rugged, reliable, compact and long-lived reactor systems designed to operate in unforgiving environments. NR is a joint DOE and Department of the Navy organization responsible for all aspects of naval nuclear propulsion.

The partnership is responsible for developing the first NASA spacecraft, the Jupiter Icy Moons Orbiter (JIMO), that will take advantage of a nuclear-reactor energy source for exploring our solar system. JIMO will visit Jupiter’s three icy moons, Ganymede, Callisto and Europa. These icy worlds, in particular Europa, are believed to have liquid-water oceans, under a thick layer of ice on their surfaces, which could potentially harbor life.

The reactor system will provide substantially more electrical power. This will greatly enhance the capability of ion-drive propulsion, the number and variety of scientific instruments on the spacecraft, the rate of data transmission, and orbital maneuvering around Jupiter’s moons.

NASA sought this partnership because NR has an enduring commitment to safety and environmental stewardship that is a requirement for an undertaking of this magnitude, ” said NASA Administrator Sean O’Keefe.

“This partnership will help ensure the safe development and use of a space-fission reactor to enable unparalleled science and discovery as we explore the solar system and beyond. This work is an integral piece of the President’s exploration agenda,” Administrator O’Keefe said.

NASA, through its newly created Office of Exploration Systems, expects that several reactor modules of the same or similar design as that required for JIMO would be developed for use on future exploration missions. NR will direct and oversee the development, design and delivery of, and operational support for these civilian reactor modules.

The Office of Nuclear Energy, Science and Technology, another DOE organization with extensive nuclear-reactor development experience, will retain responsibility for supporting NASA’s other space nuclear technology efforts, including long-term space-reactor science and technology development not associated with NR’s responsibilities.

All activities in support of NASA will be conducted as part of NR’s civilian responsibilities for the National Nuclear Security Administration, a semi-autonomous agency of DOE. Activities in support of NASA are not part of NR’s Navy responsibilities or any Department of Defense activities. This partnership with NASA is consistent with NR’s history of supporting fission-reactor work for civilian applications, including the first U.S. commercial production of electricity from nuclear power at the Shippingport Atomic Power Station.

NASA will fund all work under the partnership. Specific roles and responsibilities will be defined in Memoranda of Understanding and Agreements currently being drafted by NASA and NR. NR and the DOE Office of Nuclear Energy will also review capabilities and facilities at DOE laboratories outside NR for consideration in support of JIMO and other Project Prometheus activities.

Established in 2003, Project Prometheus is developing radioisotope electric power sources for use in space and on planets or moons, as well as new fission-reactor power sources for advanced missions into deep space requiring higher power levels for science observations, propulsion, communications and life support systems.

More information on Project Prometheus is available at:
http://spacescience.nasa.gov/missions/prometheus.htm

More information on the Jupiter Icy Moons Orbiter is available at:
http://spacescience.nasa.gov/missions/JIMO.pdf

Original Source: NASA News Release

Posted on by Fraser Cain

Mars Express Finds South Pole Water Ice

Image credit: ESA
Thanks to ESA?s Mars Express, we now know that Mars has vast fields of perennial water ice, stretching out from the south pole of the Red Planet.

Astronomers have known for years that Mars possessed polar ice caps, but early attempts at chemical analysis suggested only that the northern cap could be composed of water ice, and the southern cap was thought to be carbon dioxide ice.

Recent space missions then suggested that the southern ice cap, existing all year round, could be a mixture of water and carbon dioxide. But only with Mars Express have scientists been able to confirm directly for the first time that water ice is present at the south pole too.

Mars Express made observations with its OMEGA instrument to measure the amounts of sunlight and heat reflected from the Martian polar region. When planetary scientists analysed the data, it clearly showed that, as well as carbon dioxide ice, water ice was present too.

The results showed that hundreds of square kilometres of ?permafrost? surround the south pole. Permafrost is water ice, mixed into the soil of Mars, and frozen to the hardness of solid rock by the low Martian temperatures. This is the reason why water ice has been hidden from detection until now – because the soil with which it is mixed cannot reflect light easily and so it appears dark.

However, OMEGA looked at the surface with infrared eyes and, being sensitive to heat, clearly picked up the signature of water ice. The discovery hints that perhaps there are much larger quantities of water ice all over Mars than previously thought.

Using this data, planetary scientists now know that the south polar region of Mars can be split into three separate parts. Part one is the bright polar cap itself, a mixture of 85% highly reflective carbon dioxide ice and 15% water ice.

The second part comprises steep slopes known as ?scarps?, made almost entirely of water ice, that fall away from the polar cap to the surrounding plains. The third part was unexpected and encompasses the vast permafrost fields that stretch for tens of kilometres away from the scarps.

The OMEGA observations were made between 18 January and 11 February this year, when it was late summer for the Martian southern hemisphere and temperatures would be at their highest. Even so, that is probably only ?130 degrees Celsius and the ice that Mars Express has observed is a permanent feature of this location.

During the winter months, scientists expect that carbon dioxide from the atmosphere will freeze onto the poles, making them much larger and covering some of the water ice from view.

Mars Express and OMEGA will now continue looking for water ice and minerals across the surface of the planet. In May, another Mars Express instrument, the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), will begin collecting data, looking for water underground.

It will be particularly exciting when MARSIS looks at the south pole because, once planetary scientists know how deep the ice reaches, they will be able to calculate exactly how much water there is. Knowing this is very important to understand how Mars evolved and if it ever harboured life.

Original Source: ESA News Release

Posted on by Fraser Cain

Near Miss Today By Asteroid 2004 FH

Image credit: NASA
A small near-Earth asteroid (NEA), discovered Monday night by the NASA-funded LINEAR asteroid survey, will make the closest approach to Earth ever recorded. There is no danger of a collision with the Earth during this encounter.

The object, designated 2004 FH, is roughly 30 meters (100 feet) in diameter and will pass just 43,000 km (26,500 miles, or about 3.4 Earth diameters) above the Earth’s surface on March 18th at 5:08 PM EST (2:08 PM PST, 22:08 UTC).

On average, objects about the size of 2004 FH pass within this distance roughly once every two years, but most of these small objects pass by undetected. This particular close approach is unusual only in the sense that scientists know about it. The fact that an object as small as asteroid 2004 FH has been discovered now is mostly a matter of perseverance by the LINEAR team, who are funded by NASA to search for larger kilometer-sized NEAs, but also routinely detect much smaller objects.

Asteroid 2004 FH’s point of closest approach with the Earth will be over the South Atlantic Ocean. Using a good pair of binoculars, the object will be bright enough to be seen during this close approach from areas of Europe, Asia and most of the Southern Hemisphere.

Scientists look forward to the flyby as it will provide them an unprecedented opportunity to study a small NEA asteroid up close.

Original Source: NASA News Release

Posted on by Fraser Cain

New Detail on Cometary Jets Seen By Stardust

Image credit: NASA/JPL
On 2 January 2004, NASA’s Stardust spacecraft successfully survived flying through the coma (dust and gas cloud) surrounding comet 81P/Wild 2, captured thousands of fresh cometary dust particles released from the surface just hours before, and is now on its way home for Earth return set for January 2006.

During the flyby, the highest resolution images ever taken of a comet’s nucleus were obtained and have been the subject of intense study since the flyby. A short exposure image showing tremendous surface detail was overlain on a long exposure image taken just 10 seconds later showing jets.

“This spectacular composite image shows a surface feature unlike any other planetary surface see to date in our solar system”, says Prof Donald Brownlee, the Stardust Principal Investigator from the University of Washington. “Other than our sun, this is currently the most active planetary surface in our solar system, jetting dust and gas streams into space and leaving a trail millions of kilometers long.”

“The overall shape of the nucleus resembles a thick hamburger patty with a few bites taken out”, says Thomas Duxbury, the Stardust Project Manager from JPL. “The surface has significant relief on top of this overall shape that reflects billions of years of resurfacing from crater impacts and out gassing”.

One mystery from the close-views of Wild-2 was its pockmarks. “I looked at the images in stereo view,” said Brownlee. “One large depression has a bottom that is flat, with very steep walls [400-500 meters deep]. While any scientific evidence is only two days old,” most impact craters are expected to be bowl-shaped with much shallower aspect ratios (0.1-0.2), meaning they are five times wider than they are deep. Some of these depressions are not round, but scalloped and much deeper (aspect ratio, 0.4).

“I am from Washington state”, said Brownlee, “and when the comet is viewed in stereo pairs like that, it reminds me of Grand Cooley, with its steep cliffs and run-out areas at the bottom. Like flood areas from the Columbia River, if you were standing at the bottom of one of these comet depressions. But the floor of these comet depressions are incredibly complicated, like balls of clay have been mashed together and then etched.”

“The mission scientists with Deep Space I,” which flew by comet Borrelly, found surprising “mesas”, said Brownlee. “They speculated that these walls can sometimes face sunwards, and volatiles like ice and methane may evaporate or etch that surface. But on Wild-2, we see pits, not mesas. The two comets are quite different. We may have [with Wild-2] a young comet that evolves towards Borrelly, or vice versa.”

Three large comet jets registered on one of Stardust’s instruments, its dust counter. Three distinct peaks appeared with thousands of particle strikes each. Slightly less than an ounce of comet dust, or about a thimbleful, were collected over the spacecraft’s 12 minute pass through these large jets. “The secret of our mission is that we sample only the volatile material, that which is evaporating into space,” said Brownlee. “That’s the way we avoid any contaminants that might have left those impact-like marks on the comet’s surface. So it was better in this case to fly-through the lighter dust stream, than to land on this comet. We’d have to drive around a bit to find just the comet stuff.” In just such a science-fiction scenario of landing on a comet, the European mission, called Rosetta, will launch next month and travel to comet Churyumov-Gerasimenko in November 2014.

Preliminary scientific results obtained from the Wild 2 encounter are being presented at the Lunar and Planetary Science Conference in Houston, Texas by the Stardust science team. Stardust will bring samples of comet dust back to Earth in January 2006 to help answer fundamental questions about the origins of the solar system.

Original Source: NASA Astrobiology Magazine

Posted on by Fraser Cain

Integral Solves a Gamma Ray Mystery

Image credit: ESA
ESA’s Integral gamma-ray observatory has resolved the diffuse glow of gamma rays in the centre of our Galaxy and has shown that most of it is produced by a hundred individual sources.

Integral’s high sensitivity and pointing precision have allowed it to detect these celestial objects where all other telescopes, for more than thirty years, had seen nothing but a mysterious, blurry fog of gamma rays…

During the spring and autumn of 2003, Integral observed the central regions of our Galaxy, collecting some of the perpetual glow of diffuse low-energy gamma rays that bathe the entire Galaxy.

These gamma rays were first discovered in the mid-1970s by high-flying balloon-borne experiments. Astronomers refer to them as the ‘soft’ Galactic gamma-ray background, with energies similar to those used in medical X-ray equipment.

Initially, astronomers believed that the glow was caused by interactions involving the atoms of the gas that pervades the Galaxy. Whilst this theory could explain the diffuse nature of the emission, since the gas is ubiquitous, it failed to match the observed power of the gamma rays. The gamma rays produced by the proposed mechanisms would be much weaker than those observed. The mystery has remained unanswered for decades.

Now Integral’s superb gamma-ray telescope IBIS, built for ESA by an international consortium led by Principal Investigator Pietro Ubertini (IAS/CNR, Rome, Italy), has seen clearly that, instead of a fog produced by the interstellar medium, most of the gamma-rays are coming from individual celestial objects. In the view of previous, less sensitive instruments, these objects appeared to merge together.

In a paper published today in Nature, Francois Lebrun (CEA Saclay, Gif sur Yvette, France) and his collaborators report the discovery of 91 gamma-ray sources towards the direction of the Galactic centre. Lebrun’s team includes Ubertini and seventeen other European scientists with long-standing experience in high-energy astrophysics. Much to the team’s surprise, almost half of these sources do not fall in any class of known gamma-ray objects. They probably represent a new population of gamma-ray emitters.

The first clues about a new class of gamma-ray objects came last October, when Integral discovered an intriguing gamma-ray source, known as IGRJ16318-4848. The data from Integral and ESA’s other high-energy observatory XMM-Newton suggested that this object is a binary system, probably including a black hole or neutron star, embedded in a thick cocoon of cold gas and dust. When gas from the companion star is accelerated and swallowed by the black hole, energy is released at all wavelengths, mostly in the gamma rays.

However, Lebrun is cautious to draw premature conclusions about the sources detected in the Galactic centre. Other interpretations are also possible that do not involve black holes. For instance, these objects could be the remains of exploded stars that are being energised by rapidly rotating celestial ‘powerhouses’, known as pulsars.

Observations with another Integral instrument (SPI, the Spectrometer on Integral) could provide Lebrun and his team with more information on the nature of these sources. SPI measures the energy of incoming gamma rays with extraordinary accuracy and allows scientist to gain a better understanding of the physical mechanisms that generate them.

However, regardless of the precise nature of these gamma-ray sources, Integral’s observations have convincingly shown that the energy output from these new objects accounts for almost ninety per cent of the soft gamma-ray background coming from the centre of the Galaxy. This result raises the tantalising possibility that objects of this type hide everywhere in the Galaxy, not just in its centre.

Again, Lebrun is cautious, saying, “It is tempting to think that we can simply extrapolate our results to the entire Galaxy. However, we have only looked towards its centre and that is a peculiar place compared to the rest.”

Next on Integral’s list of things to do is to extend this work to the rest of the Galaxy. Christoph Winkler, ESA’s Integral Project Scientist, says, “We now have to work on the whole disc region of the Galaxy. This will be a tough and long job for Integral. But at the end, the reward will be an exhaustive inventory of the most energetic celestial objects in the Galaxy.”

Original Source: ESA News Release

Posted on by Fraser Cain

Space Adventures Seeking a Spaceport Location

Image credit: Space Adventures
Space Adventures, the world’s leading space tourism company, is currently exploring several locations around the world for construction of a space tourism spaceport. Current sites being considered are located in Australia, The Bahamas, Florida, Japan, Malaysia, Nevada, New Mexico, Oklahoma, Singapore and Dubai in the United Arab Emirates. Operations at the spaceport will include sub-orbital flights, a space flight training center and other activities.

“This is an ideal economic scenario for local communities. The building and then operation of a Space Adventures’ spaceport will undoubtedly bring tens of millions of dollars in the short-term and hundreds of millions in the long-term to the local economy through the increase of jobs and of tourists to the area and the required ancillary support,” said Tim Franta, space business consultant and former director of business development, Florida Space Authority. “It will be a win-win for both Space Adventures and the selected region.”

“Securing the location of a spaceport will be a progressive step for Space Adventures in its evolution from a space experiences provider to an actual space flight academy,” said Eric Anderson, president and CEO of Space Adventures. “We are aggressively seeking a location and enthusiastically look forward to the launch of the first Space Adventures’ sub-orbital flight from our spaceport in the coming years.”

The next generation spacecraft vehicles that will be used for the sub-orbital flights are now being tested. Space Adventures is the marketing and experience operations partner for several of the leading space vehicle manufacturing companies and has already taken over 100 seat reservations for explorers from around the world.

Space Adventures’ sub-orbital program will consist of a detailed four-day flight preparation and training experience. The highly focused and inspiring pre-flight agenda will familiarize each passenger with the flight program, critical vehicle systems, flight operations, zero gravity conditions, in-flight accelerations, and space flight safety procedures. On launch day, flight specialists will assist the passengers in suiting up and guiding each through the final checklist. Each flight will be directed by both a skilled-pilot and a precise computer controlled system. As each vehicle reaches their maximum altitude, the rocket engines will shutdown and the passengers will experience up to five minutes of continuous weightlessness, all the while gazing at the vast blackness of space set against the blue horizon of the Earth below.

Original Source: Space Adventures News Release

Posted on by Fraser Cain

More Details on Water Vapour Feedback

Image credit: NASA
A NASA-funded study found some climate models might be overestimating the amount of water vapor entering the atmosphere as the Earth warms. Since water vapor is the most important heat-trapping greenhouse gas in our atmosphere, some climate forecasts may be overestimating future temperature increases.

In response to human emissions of greenhouse gases, like carbon dioxide, the Earth warms, more water evaporates from the ocean, and the amount of water vapor in the atmosphere increases. Since water vapor is also a greenhouse gas, this leads to a further increase in the surface temperature. This effect is known as “positive water vapor feedback.” Its existence and size have been contentiously argued for several years.

Ken Minschwaner, a physicist at the New Mexico Institute of Mining and Technology, Socorro, N.M., and Andrew Dessler, a researcher with the University of Maryland, College Park, and NASA’s Goddard Space Flight Center, Greenbelt, Md, did the study. It is in the March 15 issue of the American Meteorological Society’s Journal of Climate. The researchers used data on water vapor in the upper troposphere (10-14 km or 6-9 miles altitude) from NASA’s Upper Atmosphere Research Satellite (UARS).

Their work verified water vapor is increasing in the atmosphere as the surface warms. They found the increases in water vapor were not as high as many climate-forecasting computer models have assumed. “Our study confirms the existence of a positive water vapor feedback in the atmosphere, but it may be weaker than we expected,” Minschwaner said.

“One of the responsibilities of science is making good predictions of the future climate, because that’s what policy makers use to make their decisions,” Dessler said. “This study is another incremental step toward improving those climate predictions,” he added.

According to Dessler, the size of the positive water vapor feedback is a key debate within climate science circles. Some climate scientists have claimed atmospheric water vapor will not increase in response to global warming, and may even decrease. General circulation models, the primary tool scientists use to predict the future of our climate, forecast the atmosphere will experience a significant increase in water vapor.

NASA’s UARS satellite was used to measure water vapor on a global scale and with unprecedented accuracy in the upper troposphere. Humidity levels in this part of the atmosphere, especially in the tropics, are important for global climate, because this is where the water vapor has the strongest impact as a greenhouse gas.

UARS recorded both specific and relative humidity in the upper troposphere. Specific humidity refers to the actual amount of water vapor in the air. Relative humidity relates to the saturation point, the amount of water vapor in the air divided by the maximum amount of water the air is capable of holding at a given temperature. As air temperatures rise, warm air can hold more water, and the saturation point of the air also increases.

In most computer models relative humidity tends to remain fixed at current levels. Models that include water vapor feedback with constant relative humidity predict the Earth’s surface will warm nearly twice as much over the next 100 years as models that contain no water vapor feedback.

Using the UARS data to actually quantify both specific humidity and relative humidity, the researchers found, while water vapor does increase with temperature in the upper troposphere, the feedback effect is not as strong as models have predicted. “The increases in water vapor with warmer temperatures are not large enough to maintain a constant relative humidity,” Minschwaner said. These new findings will be useful for testing and improving global climate models.

NASA’s Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth system science to improve prediction of climate, weather and natural hazards using the unique vantage point of space. NASA plans to launch the Aura satellite in June 2004. Along with the Terra and Aqua satellites already in operation, Aura will monitor changes in Earth’s atmosphere.

Original Source: NASA News Release

Posted on by Fraser Cain

Ulysses is Running Out of Power

Image credit: NASA
Deep space is cold. Very cold. That’s a problem–especially if you’re flying in an old spaceship. And your power supplies are waning. And the fuel lines could freeze at any moment. Oh, and by the way, you’ve got to keep flying for thirteen more years.

It sounds like a science fiction thriller, but this is really happening to the NASA/European Space Agency spacecraft Ulysses.

Ulysses was launched in 1990 on a five-year mission to study the sun. The craft gathered new data about the speed and direction of the solar wind. It discovered the 3D shape of the sun’s magnetic field. It recorded solar flares on the sun, and super-solar flares from distant neutron stars. Ulysses even flew through the tail of comet Hyakutake, an unexpected encounter that delighted astronomers.

The mission was supposed to end in 1995, but Ulysses was too successful to quit. NASA and the ESA have granted three extensions, most recently in Feb. 2004. Ulysses is scheduled to keep going until 2008, thirteen years longer than originally planned.

Ulysses’ extended mission, as before, is to study the sun. But at the moment Ulysses is far from our star. It’s having an encounter with Jupiter, studying the giant planet and its magnetic field. Sunlight out there is 25 times less intense than what we experience on Earth, and Ulysses is getting perilously cold.

Back in the 1980’s, when Ulysses was still on Earth and being assembled, mission planners knew that the spacecraft would have to endure some low temperatures. So they put dozens of heaters onboard, all powered by a Radioisotope Thermoelectric Generator, or “RTG.” These heaters have kept Ulysses comfortably warm.

But there’s a problem: the RTG is fading.

“The power output of the RTG has been dropping since the spacecraft was launched,” says Nigel Angold, the Ulysses ESA Spacecraft Operations Manager at JPL. RTG power naturally fades as its radioactive source decays. That’s as expected. What planners didn’t expect was 13 years of extra operations.

“When Ulysses was launched in 1990 the RTG produced 285 watts. Now it’s down to 207 watts–barely enough power to run the science instruments and the heaters at the same time,” notes Angold.

Inside Ulysses the temperature varies from place to place. “Many of the science instruments are already below freezing (0 C),” says Ulysses thermal engineer Fernando Castro. “That’s OK, because they can operate at low temperature.” But the fuel lines are another matter. They’re hovering about 3 degrees above zero, “and if they freeze we’re in trouble.”

Fuel lines are critical to the mission. They deliver hydrazine propellant to the ship’s eight thrusters. Every week or so, ground controllers fire the thrusters to keep Ulysses’ radio antenna pointing toward Earth. The thrusters won’t work if the hydrazine freezes. No thrusters means no communication. The mission would be lost.

About eight meters of fuel line snake through the spaceship. Every twist and turn is a possible cold spot, a place where the hydrazine can begin to solidify. “If the hydrazine freezes anywhere, I don’t know if we can safely thaw it again,” worries Castro. When hydrazine thaws, it expands, possibly enough to rupture the fuel lines. Ulysses’ propellant would fizzle uselessly into space.

The temperature at any given point along the fuel lines is bewilderingly sensitive to what’s going on elsewhere in the spacecraft. Turning on a scientific instrument “here” might cause a chill “over there,” because it takes power away from one of the heaters. Firing a thruster, playing back or recording data: almost anything could upset Ulysses’ delicate thermal balance.

Above: The complicated interior of Ulysses. Dark blocks are science instruments and other devices. Fuel lines, denoted by red, blue and green, lead from a central hydrazine tank to the thrusters. Click here to view areas most vulnerable to freezing.

Even the simple act of sending the spacecraft a message can cause problems. Systems engineer Andy McGarry recalls, “last month we were sending some new commands to Ulysses when the temperature began to drop, as much as 0.8 degrees C near the fuel lines. We were less than a degree from the freezing point of hydrazine–too close for comfort.”

Engineers quickly figured out the problem. “All of Ulysses’ science instruments had been activated to study Jupiter,” explains McGarry, “and this was straining the RTG to its limit.” Ulysses would have trouble supporting even one more device. But when a signal arrived from Earth, another device did turn on, automatically: the decoder, which translates radio signals into a stream of binary ones and zeros understood by Ulysses’ computers. “The decoder was stealing power from the heaters.”

Since then ground controllers have learned to keep their transmissions to Ulysses brief, so the temperature can’t fall very far.

Ulysses is about to turn away from Jupiter and head back to the sun. Eventually solar heating will keep the hydrazine warm, and onboard heaters can be turned off, “but that won’t happen until 2007,” says Angold. Meanwhile, engineers at JPL keep a constant watch on the spacecraft.

Mission scientist Steve Suess at the NASA Marshall Space Flight Center believes it’s worth the effort. “The extended mission gives us a chance to learn a lot more about the sun.” Of special interest is the Solar Minimum. Solar activity waxes and wanes every 11 years, he explains. Ulysses studied the sun’s quiet phase, Solar Minimum, between 1994 and 1995. Now Ulysses gets to do it again. “The next Solar Minimum is due around 2006,” says Suess, “but it won’t be the same as before.” In 2001 the sun’s magnetic field flipped. The north pole shifted south, and vice versa. Magnetically speaking, the sun is now upside down. How will that affect Solar Minimum?

Perhaps Ulysses will find out ? if it doesn’t freeze to death first.

Original Source: NASA Science Story

Posted on by Fraser Cain

The Origins of Oxygen on Earth

Image credit: NASA
Christopher Chyba is the principal investigator for The SETI Institute lead team of the NASA Astrobiology Institute. Chyba formerly headed the SETI Institute’s Center for the Study of Life in the Universe. His NAI team is pursuing a wide range of research activities, looking at both life’s beginnings on Earth and the possibility of life on other worlds. Astrobiology Magazine’s managing editor, Henry Bortman, spoke recently with Chyba about several of his team’s projects that will explore the origin and significance of oxygen in Earth’s atmosphere.

Astrobiology Magazine: Many of the projects that members of your team will be working on have to do with oxygen in Earth’s atmosphere. Today oxygen is a significant component of the air we breathe. But on early Earth, there was very little oxygen in the atmosphere. There is a great deal of debate about just how and when the planet’s atmosphere became oxygenated. Can you explain how your team’s research will approach this question?

Christopher Chyba: The usual story, with which you’re probably familiar, is that after oxygenic photosynthesis evolved, there was then a huge biological source of oxygen on early Earth. That’s the usual view. It may be right, and what’s usually the case in these kinds of arguments is not whether one effect is right or not. Probably many effects were active. It’s a question of what was the dominant effect, or whether there were several effects of comparable importance.

SETI Institute researcher Friedemann Freund has a completely non-biological hypothesis about the rise of oxygen, which has some experimental support from laboratory work that he’s done. The hypothesis is that, when rocks solidify from magma, they incorporate small amounts of water. Cooling and subsequent reactions leads to the production of peroxy links (consisting of oxygen and silicon atoms) and molecular hydrogen in the rocks.

Then, when the igneous rock is subsequently weathered, the peroxy links produce hydrogen peroxide, which decomposes into water and oxygen. So, if this is right, simply weathering igneous rocks is going to be a source of free oxygen into the atmosphere. And if you look at some of the quantities of oxygen that Friedemann is able to release from rocks in well-controlled situations in his initial experiments, it might be that this was a substantial and significant source of oxygen on early Earth.

So even apart from photosynthesis, there might be a kind of natural source of oxygen on any Earth-like world that had igneous activity and liquid water available. This would suggest that the oxidation of the surface might be something that you expect to occur, whether photosynthesis happens early or late. (Of course, the timing of this depends on oxygen sinks as well.) I emphasize that’s all a hypothesis at this point, for much more careful investigation. Friedemann’s done only pilot experiments so far.

One of the interesting things about Friedemann’s idea is that it suggests there might be an important source of oxygen on planets completely independent of biological evolution. So there might be a natural driver towards the oxidation of the surface of a world, with all the ensuing consequences for evolution. Or maybe not. The point is to do the work and find out.

Another component of his work, which Friedemann will do with the microbiolologist Lynn Rothschild of NASA Ames Research Center, has to do with this question of whether in environments associated with weathered igneous rocks and the production of oxygen, you could have created micro-environments that would have allowed certain microorganisms living in those environments to have pre-adapted to an oxygen-rich environment. They’ll be doing work with microorganisms to try to address that question.

AM: Emma Banks will be looking at chemical interactions in the atmosphere of Saturn’s moon Titan. How does that tie into understanding oxygen on early Earth?

CC: Emma’s looking at another abiotic way that might be important in oxidizing a world’s surface. Emma does chemical computational models, all the way down to the quantum mechanical level. She does them in a number of contexts, but what’s relevant to this proposal has to do with haze formation.

On Titan – and possibly on the early Earth as well, depending on your model for the atmosphere of the early Earth – there’s a polymerization of methane [the combination of methane molecules into larger hydrocarbon-chain molecules] in the upper atmosphere. Titan’s atmosphere is several percent methane; almost all the rest of it is molecular nitrogen. It’s bombarded with ultraviolet light from the sun. It’s also bombarded with charged particles from Saturn’s magnetosphere. The effect of that, acting on the methane, CH4 , is to break the methane up and polymerize it into longer-chain hydrocarbons.

If you start polymerizing methane into longer and longer carbon chains, each time you add another carbon onto the chain, you’ve got to get rid of some hydrogen. For example, to go from CH4 (methane) to C2H6, (ethane) you have to get rid of two hydrogens. Hydrogen is an extremely light atom. Even if it makes H2, that’s an extremely light molecule, and that molecule’s lost off the top of Titan’s atmosphere, just as it’s lost off the top of the Earth’s atmosphere. If you bleed hydrogen off the top of your atmosphere, the net effect is to oxidize the surface. So it’s another way that gives you a net oxidation of a world’s surface.

Emma’s interested in this primarily with respect to what takes place on Titan. But it’s also potentially relevant as a kind of global oxidizing mechanism for the early Earth. And, bringing nitrogen into the picture, she’s interested in the potential production of amino acids out of these conditions.

AM: One of the mysteries about early life on Earth is how it survived the damaging effects of ultraviolet (UV) radiation before there was enough oxygen in the atmosphere to provide an ozone shield. Janice Bishop, Nathalie Cabrol and Edmond Grin, all of whom are with the SETI Institute, are exploring some of these strategies.

CC: And there are a lot of potential strategies there. One is just being deep enough below the surface, whether you’re talking about the land or the sea, to be completely shielded. Another is to be shielded by minerals within the water itself. Janice and Lynn Rothschild are working on a project that is examining the role of ferric oxide minerals in water as a kind of UV shield.

In the absence of oxygen the iron in water would be present as ferric oxide. (When you have more oxygen, the iron oxidizes further; it becomes ferrous and drops out.) Ferric oxide could potentially have played the role of an ultraviolet shield in the early oceans, or in early ponds or lakes. To investigate how good it is as a potential UV shield, there are some measurements you might want to make, including measurements in natural environments, such as in Yellowstone. And once again there’s a microbiological component to the work, with Lynn’s involvement.

This is related to the project that Nathalie Cabrol and Edmond Grin are pursuing, from a different perspective. Nathalie and Edmond are very interested in Mars. They are both on the Mars Exploration Rover science team. In addition to their Mars work, Nathalie and Edmond explore environments on Earth as Mars analog sites. One of their topics of investigation is strategies for survival in high-UV environments. There’s a lake six kilometers high on Licancabur (a dormant volcano in the Andes). We now know there’s microscopic life in that lake. And we’d like to know what are its strategies for surviving in the high-UV environment there? And that’s a different, very empirical way of getting at this question of how life survived in the high-UV environment that existed on early Earth.

These four projects are all coupled, because they have to do with the rise of oxygen on early Earth, how organisms survived before there was substantial oxygen in the atmosphere, and then, how all this relates to Mars.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Universe Today Maintenance Thursday

If you had problems accessing Universe Today yesterday, don’t worry, you weren’t alone. I was “lucky” enough to end up on the homepage of Google News for the Sedna story. The resulting traffic brought my webserver to its knees. I had a chat with my service provider and they’ve recommended some upgrades to the server to better handle future traffic spikes. They’ll be installing the new hardware on Thursday at 1500 UTC (10 am EST), so the website will be down for 1-2 hours. Okay, Google… bring it on.

Thanks to everyone who donated over the weekend… it was good timing. 🙂

Fraser Cain
Publisher
Universe Today