Time Space Science

Data collected during two close flybys of Saturn's moon Enceladus by NASA's Cassini spacecraft add more fuel to the fire about the Saturnian ice world containing sub-surface liquid water. The data collected by Cassini's Ion and Neutral Mass Spectrometer during Enceladus flybys in July and Oct. 2008, were released in the July 23 issue of the journal Nature.

"When Cassini flew through the plume erupting from Enceladus on October 8 of last year, our spectrometer was able to sniff out many complex chemicals, including organic ones, in the vapor and icy particles," said Hunter Waite, the Cassini Ion and Neutral Mass Spectrometer Lead Scientist from the Southwest Research Institute in San Antonio, Texas. "One of the chemicals definitively identified was ammonia."

On Earth, the presence of ammonia means the potential for sparkling clean floors and counter tops. In space, the presence of ammonia provides strong evidence for the existence of at least some liquid water.

How could ammonia equate to liquid water inside an ice-covered moon in one of the chillier neighborhoods of our solar system? As many a homeowner interested in keeping their abodes spick and span know, ammonia promptly dissolves in water. But what many people do not realize is that ammonia acts as antifreeze, keeping water liquid at lower temperatures than would otherwise be possible. With the presence of ammonia, water can exist in a liquid state to temperatures as low as 176 degrees Kelvin (-143 degrees Fahrenheit).

"Given that temperatures in excess of 180 Kelvin (-136 degrees Fahrenheit) have been measured near the fractures on Enceladus where the jets emanate, we think we have an excellent argument for a liquid water interior," said Waite.

Cassini discovered water vapor and particles spewing from Enceladus in 2005. Since then, scientists have been trying to determine if the plume originates from a liquid source inside the moon or is due to other causes.

"Ammonia is sort of a holy grail for icy volcanism," said William McKinnon, a scientist from Washington University in Saint Louis, Missouri. "This is the first time we've found it for sure on an icy satellite of a giant planet. It is probably everywhere in the Saturn system."

Just how much water is contained within Enceladus' icy interior is still up for debate. So far, Cassini has made five flybys of Enceladus, one of the chief targets for Cassini's extended mission. Two close flybys are scheduled for November of this year, and two more close flybys are scheduled for April and May or 2010. Data collected during these future flybys may help settle the debate.

"Where liquid water and organics exist, is there life?" asked Jonathan Lunine a Cassini scientist from the University of Arizona, Tucson. "Such is the case for Earth; what was found on Enceladus bolsters this moon's promise for containing potential habitable environments."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Cassini orbiter was designed, developed and assembled at JPL. JPL manages the mission for the Science Mission Directorate at NASA Headquarters in Washington.

http://www.jpl.nasa.gov/

The eerie beauty of the northern and southern lights has evoked visions of the supernatural for centuries: foxes of fire whisking their tales, the fighting souls of dead warriors or ancestors dancing around a ceremonial fire.

The English poet Sir Walter Scott in 1805 conjured up otherworldly beings when he wrote, "He knew, by the streamers that shot so bright, That spirits were riding the northern light."

But it was a French scientist, not a poet, who named the sight after Roman gods. In 1621, Pierre Cassendi paired Aurora, goddess of dawn, with Boreas, god of the north wind, to christen the northern lights “aurora borealis.” Those centered above the South Pole are called aurora australis for “southern dawn.”

Even today, scientists and forecasters at NOAA’s Space Weather Prediction Center in Boulder, Colo., look beyond the Earth itself for the first step in a chain of events that ultimately paints brilliant hues across the night sky at opposite ends of the planet.

Anatomy of an Aurora

Deep within the Sun, 93 million miles away, roiling plasma rises and bursts through the solar atmosphere, sometimes thrusting highly charged protons and electrons our way. When this so-called solar wind arrives near Earth, it energizes protons and electrons trapped in the planet’s magnetic field.

These charged particles then travel down magnetic field lines, like beads slipping along a string, into Earth’s upper atmosphere near the poles. There the particles in turn excite atoms and molecules of oxygen, nitrogen, and other atmospheric gases. As these atoms relax back down into their normal state, they release the excess energy as visible light, forming an aurora oval loosely centered on the magnetic pole.

During an aurora, vivid arcs, curls, waves and bands of green, red, and sometimes blue dance across the sky for minutes or hours, peaking near midnight — all between 60 and 600 miles above the ground.

Many people think auroras are rare events, but there’s almost always an aurora of some size in the sky near the poles. Seeing one is another matter.

Auroras are most often visible in regions bordering the Arctic Circle: Canada, Alaska, northern Greenland, the Scandinavian coast, and Siberia. In the south, you need to be visiting Antarctica to see an aurora frequently. But the larger the solar storm reaching Earth’s upper atmosphere, the farther the aurora extends from the poles. Residents of New England or southern Chile might see an aurora every few years. If you live in Florida or Italy, you’d be lucky to see an aurora once in your lifetime.

How Space Weather Affects Us

One of the nation’s critical operations centers, NOAA’s Space Weather Prediction Center keeps a close eye on solar activity that precedes an aurora. When a major storm explodes on the sun, followed by a suddenly intensified solar wind heading toward Earth, the center alerts airlines, the military, the communications industry, power companies and the media that a storm is on its way.

Why do NOAA scientists care about this odd “weather” on the sun and in space? NOAA monitors solar storms because they can disrupt satellite functions, power grid operations, GPS signals, high-frequency communications used by airlines and the military, and other space-based technologies that we depend on. Solar radiation could also threaten astronauts’ safety if they happen to be outside the space shuttle as it zooms past.

Visit the Space Weather Prediction Center’s aurora Web site to view the current shape and size of the auroras around the two poles. If the auroras shown there are exceptionally large and you’re in a far northern or far southern latitude, look for those spirits hurtling across the midnight sky!

Tips on Seeing an Aurora

Best time of night: 10:00 p.m. to 2:00 a.m.
Best conditions: clear night with no moon and far from light pollution
Best season: mid-winter
Best phase of the solar cycle: maximum
Best years in the sun’s current cycle: 2012 to 2013
Best position on Earth: far northern or southern latitudes


http://www.noaa.gov/

The "coming of age" of galaxies and black holes has been pinpointed, thanks to new data from NASA's Chandra X-ray Observatory and other telescopes. This discovery helps resolve the true nature of gigantic blobs of gas observed around very young galaxies.

About a decade ago, astronomers discovered immense reservoirs of hydrogen gas -- which they named "blobs" – while conducting surveys of young distant galaxies. The blobs are glowing brightly in optical light, but the source of immense energy required to power this glow and the nature of these objects were unclear.

A long observation from Chandra has identified the source of this energy for the first time. The X-ray data show that a significant source of power within these colossal structures is from growing supermassive black holes partially obscured by dense layers of dust and gas. The fireworks of star formation in galaxies are also seen to play an important role, thanks to Spitzer Space Telescope and ground-based observations.

"For ten years the secrets of the blobs had been buried from view, but now we've uncovered their power source," said James Geach of Durham University in the United Kingdom, who led the study. "Now we can settle some important arguments about what role they played in the original construction of galaxies and black holes."

Galaxies are believed to form when gas flows inwards under the pull of gravity and cools by emitting radiation. This process should stop when the gas is heated by radiation and outflows from galaxies and their black holes. Blobs could be a sign of this first stage, or of the second.

Based on the new data and theoretical arguments, Geach and his colleagues show that heating of gas by growing supermassive black holes and bursts of star formation, rather than cooling of gas, most likely powers the blobs. The implication is that blobs represent a stage when the galaxies and black holes are just starting to switch off their rapid growth because of these heating processes. This is a crucial stage of the evolution of galaxies and black holes - known as "feedback" - and one that astronomers have long been trying to understand.

"We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth," said coauthor Bret Lehmer, also of Durham. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day."

Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed "SSA22." These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15% of its current age.

In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes - a point-like source with luminous X-ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation.

The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations.

Besides explaining the power source of the blobs, these results help explain their future. Under the heating scenario, the gas in the blobs will not cool down to form stars but will add to the hot gas found between galaxies. SSA22 itself could evolve into a massive galaxy cluster.

"In the beginning the blobs would have fed their galaxies, but what we see now are more like leftovers," said Geach. "This means we'll have to look even further back in time to catch galaxies and black holes in the act of forming from blobs."

These results will appear in the July 10 issue of the Astrophysical Journal. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.


http://chandra.harvard.edu/

A comprehensive review by leading scientists about our solar system which speculates on the possibility of life on other planets has been published.

Solar System Update brings together the work of 19 physicists, astronomers, and climatologists from Europe and the USA in 12 chapters on the sun, the main planets and comets.

The book, co-authored by Dr Philippe Blondel, of the University of Bath, highlights the many recent discoveries and in particular the amount of water, one of the essentials for life, found in the solar system.

Recent studies have revealed ice in craters on Mercury, the closest planet to the sun, and that liquid water may once have existed on the surface of Mars, and may still be there underground.

In addition, liquid water may exist on moons around Jupiter, in particular Europa, Ganymede and Callisto, underneath a surface of ice.

In his chapter The Habitability of Mars: Past and Present, Thomas McCollom, of the Center for Astrobiology at the University of Colorado, USA, says that though the temperatures on Mars, as low as minus 120 Centigrade, mean that water cannot exist on the surface, there may be a "planet-wide liquid aquifer at some depth in its crust." There is also geological evidence that water has flowed on the surface in the past.

"It seems increasingly apparent that habitable environments very likely exist on Mars today, and may have been considerably more diverse and abundant in the past," he writes.

In his chapter The Icy Moons of Jupiter, Richard Greenberg, of the Department of Planetary Sciences at the University of Arizona, USA, says: "There is an unusually strong motivation to continue to pursue studies of the icy satellites."

He says that three large moons of Jupiter "probably have liquid water layers, and one, Europa, almost certainly has an ocean just below the surface. Naturally liquid water raises the possibility of extraterrestrial life."

However, if the surface ice were very thick, this would cut the water below off from oxygen and sunlight which are important for most forms of life on Earth, and so might have prevented life from developing.

Dr Blondel, who works in the University of Bath's Department of Physics, took 18 months to edit the book, with his co-editor Dr John Mason.

"This book sets out how much water and ice there is in the solar system," said Dr Blondel. "This obviously has implications for our search for extra-terrestrial life.

"By understanding better how the climates of planets like Mars and Venus have evolved, we can understand more about climate change on Earth.

"For instance, the very hot and cloudy climate of Venus is likely to have developed after a runaway greenhouse effect, and the more we know about this the more we can understand some of the challenges caused by our climate change on Earth. "


http://www.bath.ac.uk/

A novel bacterium -- trapped more than three kilometres under glacial ice in Greenland for over 120,000 years -- may hold clues as to what life forms might exist on other planets.

Dr Jennifer Loveland-Curtze and a team of scientists from Pennsylvania State University report finding the novel microbe, which they have called Herminiimonas glaciei, in the current issue of the International Journal of Systematic and Evolutionary Microbiology. The team showed great patience in coaxing the dormant microbe back to life; first incubating their samples at 2˚C for seven months and then at 5˚C for a further four and a half months, after which colonies of very small purple-brown bacteria were seen.

H. glaciei is small even by bacterial standards – it is 10 to 50 times smaller than E. coli. Its small size probably helped it to survive in the liquid veins among ice crystals and the thin liquid film on their surfaces. Small cell size is considered to be advantageous for more efficient nutrient uptake, protection against predators and occupation of micro-niches and it has been shown that ultramicrobacteria are dominant in many soil and marine environments.

Most life on our planet has always consisted of microorganisms, so it is reasonable to consider that this might be true on other planets as well. Studying microorganisms living under extreme conditions on Earth may provide insight into what sorts of life forms could survive elsewhere in the solar system.

"These extremely cold environments are the best analogues of possible extraterrestrial habitats", said Dr Loveland-Curtze, "The exceptionally low temperatures can preserve cells and nucleic acids for even millions of years. H. glaciei is one of just a handful of officially described ultra-small species and the only one so far from the Greenland ice sheet; studying these bacteria can provide insights into how cells can survive and even grow under extremely harsh conditions, such as temperatures down to -56˚C, little oxygen, low nutrients, high pressure and limited space."

"H. glaciei isn't a pathogen and is not harmful to humans", Dr Loveland-Curtze added, "but it can pass through a 0.2 micron filter, which is the filter pore size commonly used in sterilization of fluids in laboratories and hospitals. If there are other ultra-small bacteria that are pathogens, then they could be present in solutions presumed to be sterile. In a clear solution very tiny cells might grow but not create the density sufficient to make the solution cloudy."


http://www.sgm.ac.uk/

A team of NASA and university scientists has achieved the first definitive detection of methane in the atmosphere of Mars. This discovery indicates the planet is either biologically or geologically active.


The team found methane in the Martian atmosphere by carefully observing the planet throughout several Mars years with NASA's Infrared Telescope Facility and the W.M. Keck telescope, both at Mauna Kea, Hawaii. The team used spectrometers on the telescopes to spread the light into its component colors, as a prism separates white light into a rainbow. The team detected three spectral features called absorption lines that together are a definitive signature of methane.

"Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas," said Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md. "At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif." Mumma is lead author of a paper describing this research that will appear in Science Express on Thursday.

Methane, four atoms of hydrogen bound to a carbon atom, is the main component of natural gas on Earth. Astrobiologists are interested in these data because organisms release much of Earth's methane as they digest nutrients. However, other purely geological processes, like oxidation of iron, also release methane.

"Right now, we do not have enough information to tell whether biology or geology -- or both -- is producing the methane on Mars," Mumma said. "But it does tell us the planet is still alive, at least in a geologic sense. It is as if Mars is challenging us, saying, 'hey, find out what this means.' "

If microscopic Martian life is producing the methane, it likely resides far below the surface where it is warm enough for liquid water to exist. Liquid water is necessary for all known forms of life, as are energy sources and a supply of carbon.

"On Earth, microorganisms thrive about 1.2 to 1.9 miles beneath the Witwatersrand basin of South Africa, where natural radioactivity splits water molecules into molecular hydrogen and oxygen," Mumma said. "The organisms use the hydrogen for energy. It might be possible for similar organisms to survive for billions of years below the permafrost layer on Mars, where water is liquid, radiation supplies energy, and carbon dioxide provides carbon. Gases, like methane, accumulated in such underground zones might be released into the atmosphere if pores or fissures open during the warm seasons, connecting the deep zones to the atmosphere at crater walls or canyons."

It is possible a geologic process produced the Martian methane, either now or eons ago. On Earth, the conversion of iron oxide into the serpentine group of minerals creates methane, and on Mars this process could proceed using water, carbon dioxide and the planet's internal heat. Although there is no evidence of active volcanism on Mars today, ancient methane trapped in ice cages called clathrates might be released now.

"We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane," said co-author Geronimo Villanueva of the Catholic University of America in Washington. "The plumes were emitted during the warmer seasons, spring and summer, perhaps because ice blocking cracks and fissures vaporized, allowing methane to seep into the Martian air."

According to the team, the plumes were seen over areas that show evidence of ancient ground ice or flowing water. Plumes appeared over the Martian northern hemisphere regions such as east of Arabia Terra, the Nili Fossae region, and the south-east quadrant of Syrtis Major, an ancient volcano about 745 miles across.

One method to test whether life produced this methane is by measuring isotope ratios. Isotopes of an element have slightly different chemical properties, and life prefers to use the lighter isotopes. A chemical called deuterium is a heavier version of hydrogen. Methane and water released on Mars should show distinctive ratios for isotopes of hydrogen and carbon if life was responsible for methane production. It will take future missions, like NASA's Mars Science Laboratory, to discover the origin of the Martian methane.

The research was funded by the Planetary Astronomy Program at NASA Headquarters in Washington and the Astrobiology Institute at NASA's Ames Research Center in Moffett Field, Calif. The University of Hawaii manages NASA's Infrared Telescope Facility.

http://www.nasa.gov/centers/goddard/home/index.html

A University of Colorado at Boulder research team has discovered the first definitive evidence of shorelines on Mars, an indication of a deep, ancient lake there and a finding with implications for the discovery of past life on the Red Planet.
Estimated to be more than 3 billion years old, the lake appears to have covered as much as 80 square miles and was up to 1,500 feet deep -- roughly the equivalent of Lake Champlain bordering the United States and Canada, said CU-Boulder Research Associate Gaetano Di Achille, who led the study. The shoreline evidence, found along a broad delta, included a series of alternating ridges and troughs thought to be surviving remnants of beach deposits.

"This is the first unambiguous evidence of shorelines on the surface of Mars," said Di Achille. "The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago."

A paper on the subject by Di Achille, CU-Boulder Assistant Professor Brian Hynek and CU-Boulder Research Associate Mindi Searls, all of the Laboratory for Atmospheric and Space Physics, has been published online in Geophysical Research Letters, a publication of the American Geophysical Union.

Images used for the study were taken by a high-powered camera known as the High Resolution Imaging Science Experiment, or HiRISE. Riding on NASA's Mars Reconnaissance Orbiter, HiRISE can resolve features on the surface down to one meter in size from its orbit 200 miles above Mars.

An analysis of the HiRISE images indicate that water carved a 30-mile-long canyon that opened up into a valley, depositing sediment that formed a large delta. This delta and others surrounding the basin imply the existence of a large, long-lived lake, said Hynek, also an assistant professor in CU-Boulder's geological sciences department. The lake bed is located within a much larger valley known as the Shalbatana Vallis.

"Finding shorelines is a Holy Grail of sorts to us," said Hynek.

In addition, the evidence shows the lake existed during a time when Mars is generally believed to have been cold and dry, which is at odds with current theories proposed by many planetary scientists, he said. "Not only does this research prove there was a long-lived lake system on Mars, but we can see that the lake formed after the warm, wet period is thought to have dissipated."

Planetary scientists think the oldest surfaces on Mars formed during the wet and warm Noachan epoch from about 4.1 billion to 3.7 billion years ago that featured a bombardment of large meteors and extensive flooding. The newly discovered lake is believed to have formed during the Hesperian epoch and postdates the end of the warm and wet period on Mars by 300 million years, according to the study.

The deltas adjacent to the lake are of high interest to planetary scientists because deltas on Earth rapidly bury organic carbon and other biomarkers of life, according to Hynek. Most astrobiologists believe any present indications of life on Mars will be discovered in the form of subterranean microorganisms.

But in the past, lakes on Mars would have provided cozy surface habitats rich in nutrients for such microbes, Hynek said.

The retreat of the lake apparently was rapid enough to prevent the formation of additional, lower shorelines, said Di Achille. The lake probably either evaporated or froze over with the ice slowly turning to water vapor and disappearing during a period of abrupt climate change, according to the study.

Di Achille said the newly discovered pristine lake bed and delta deposits would be would be a prime target for a future landing mission to Mars in search of evidence of past life.

"On Earth, deltas and lakes are excellent collectors and preservers of signs of past life," said Di Achille. "If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past."


http://www.colorado.edu/