Frozen Bacteria Repair Own DNA for Millennia

Mason Inman
from National Geographic News

Bacteria can survive in deep freeze for hundreds of thousands of years by staying just alive enough to keep their DNA in good repair, a new study says.

In earlier work, researchers had found ancient bacteria in permafrost and in deep ice cores from Antarctica.

These bacteria, despite being trapped for millennia, were able to be revived and grown in the lab.

Some researchers had thought that bacteria would have to turn into dormant spores to survive for so long.

But if bacteria merely went dormant, metabolism would stop and various environmental factors would begin damaging their DNA.

Like an ancient scroll that's crumbling apart, the DNA becomes so damaged that it's indecipherable after about a hundred thousand years. Then the cells can't ever reproduce and the bacteria are effectively dead.

"Our results show that the best way to survive for a long time is to keep up metabolic activity," said Eske Willerslev, lead study author and a researcher at the University of Copenhagen in Denmark.

Doing this "allows for continuous DNA repair," Willerslev added.

The work suggests that if bacterial life existed on Mars or on Jupiter's moon Europa, it might still survive locked in icy soils.

The new study appears this week in the online advance edition of the Proceedings of the National Academy of Sciences.

Living, Just Barely

The new study examined DNA from bacteria found in permafrost from Siberia in Russia and Canada. The permafrost dated back to about a half-million years ago.

What the scientists found is that the bacteria appear to have kept up their metabolism.

These barely living bacteria did not seem to be reproducing, but they were still taking in nutrients and giving off carbon dioxide, like humans do when they breathe.

The bacteria were using some of these resources to keep their DNA in good shape, the study authors said.

But the researchers found that bacteria couldn't keep chugging along like this forever.

"You see a large diversity [of bacteria] in the modern samples, and as you get older and older, the diversity declines," Willerslev said.

The amount of carbon dioxide the bacteria gave off also dropped with age.

The limit for life in the permafrost is somewhere around 600,000 years old, the researchers say.

In older permafrost, the team couldn't detect any carbon dioxide emissions or any large pieces of DNA indicative of living bacteria.

By about 750,000 years old, the bacteria trapped in the permafrost seemed to be completely dead.

Soil vs. Ice

Some scientists have claimed to be able to revive far older bacteria preserved in amber or salts, but Willerslev has doubts about these results.

"I've been extremely skeptical about these previous results," Willerslev said.

But in the much colder environments of Mars or Europa, life might be able to survive while frozen for much longer, Willerslev said.

At those lower temperatures, DNA damage would accumulate more slowly.

So the new results "could suggest that if you had similar life on Mars, it could exist for much longer," he said.

Brent Christner of Louisiana State University welcomes the new results, which he finds convincing.

Christner and others have been studying ancient ice from deep in the Antarctic ice sheet and have found live bacteria there that have been frozen in place for perhaps one to two million years.

These ancient bacteria seemed to be repairing themselves, but the team didn't have direct evidence showing how the microbes were surviving so long.

"This study confirms and corroborates everything we've been finding with ancient glacial ice," Christner said.

Still, Willerslev is cautious about making this connection.

Glacial ice, he said, "is a completely different environment from permafrost, which is basically frozen soil" and contains lots of nutrients.

Supersonic "Hail" Seeds Star Systems With Water

John Roach
from National Geographic News

Evidence of water vapor "raining down" on a newly forming star system is offering the first direct look at how water likely gets incorporated into planets, NASA researchers announced.

(Related: "First Proof of Wet 'Hot Jupiter' Outside Solar System" [July 11, 2007].)

The water—enough to fill Earth's oceans five times over—falls at supersonic speeds in the form of a hail-like substance from the envelope of dust and gas that gave birth to the star.

The hail vaporizes when it smacks into the dusty disk around the embryonic star where planets are thought to take shape, according to models that best explain the observed data.

"This is the first time we've ever seen the process by which the surrounding envelope's material arrives at the disk," said Dan Watson, an astrophysicist at the University of Rochester in New York.

Watson is lead author of a paper describing the discovery in tomorrow's issue of the journal Nature.

"Since the disk is what's eventually going to give rise to the planetary system around the star, what we are seeing is the process by which that disk formed and therefore the initial conditions of planetary formation."

Star Development

The new work is based on observations of an embryonic star system taken with NASA's Spitzer Space Telescope (see images of stellar nurseries captured by Spitzer).

Astronomers observe such protostar systems in the infrared spectrum, because visible light is easily absorbed by the systems' dusty environments, making them invisible to the naked eye.

Water vapor emits a distinctive spectrum in infrared light.

The protostar lies about a thousand light-years from Earth in a cloud gas and dust. The whole system is called NGC 1333-IRAS 4B, or IRAS 4B for short.

The star is a warm, dense blob of material at the core of the cloud. A disk of planet-forming material is believed to circle the blob.

The radius of the disk is just larger than the distance between Pluto and the sun: about 3.6 billion miles (5.8 billion kilometers).

Based on their data, Watson and his colleagues say that the surface of the disk is -153 degrees Fahrenheit (-103 degrees Celsius).

While this seems frigid by Earth standards, Watson explained, the properties of water are different at the atmospheric pressure of the protostar, which is about a billionth of the pressure at sea level on Earth.

In addition, material equal to 23 times the mass of Earth arrives at the disk each year, Watson said.

"That's the material that's heating on arrival and then gradually cooling as it joins the lower parts of the disk," he said.

"This is very wet stuff. The original state is very wet," he added. "There's plenty of water to make a solar system out of."

Right Angle

Of the 30 embryonic star systems observed with Spitzer, only IRAS 4B showed signs of water vapor.

According to Watson, this is most likely because the protostar's axis points almost directly at Earth.

"The other 29 could very well have just as much water emission as IRAS 4B, but they are turned the wrong way and you can't see them," he said.

The team has already identified hundreds more protostar systems like IRAS 4B and plans to observe them with the Spitzer telescope, including more stars that exhibit this rare orientation.

New View of Doomed Star

Credit: X-ray: NASA/CXC/GSFC/M.Corcoran et al.; Optical: NASA/STScI

Eta Carinae is a mysterious, extremely bright and unstable star located a mere stone's throw - astronomically speaking - from Earth at a distance of only about 7,500 light years. The star is believed to be consuming its nuclear fuel at an incredible rate, while quickly drawing closer to its ultimate explosive demise. When Eta Carinae does explode, it will be a spectacular fireworks display seen from Earth, perhaps rivaling the moon in brilliance. Its fate has been foreshadowed by the recent discovery of SN2006gy, a supernova in a nearby galaxy that was the brightest stellar explosion ever seen. The erratic behavior of the star that later exploded as SN2006gy suggests that Eta Carinae may explode at any time.

Eta Carinae, a star between 100 and 150 times more massive than the Sun, is near a point of unstable equilibrium where the star's gravity is almost balanced by the outward pressure of the intense radiation generated in the nuclear furnace. This means that slight perturbations of the star might cause enormous ejections of matter from its surface. In the 1840s, Eta Carinae had a massive eruption by ejecting more than 10 times the mass of the sun, to briefly become the second brightest star in the sky. This explosion would have torn most other stars to pieces but somehow Eta Carinae survived.

The latest composite image shows the remnants of that titanic event with new data from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The blue regions show the cool optical emission, detected by Hubble, from the dust and gas thrown off the star. This debris forms a bipolar shell around the star, which lies near the brightest point of the optical emission. This bipolar shell is itself surrounded by a ragged cloud of fainter material. An unusual jet points from the star to the upper left.

Chandra's data, depicted in orange and yellow, shows the X-ray emission produced as material thrown off Eta Carinae rams into nearby gas and dust, heating gas to temperatures in excess of a million degrees. Animation of Massive Star Explosion This hot shroud extends far beyond the cooler, optical nebula and represents the outer edge of the interaction region. The X-ray observations show that the ejected outer material is enriched by complex atoms, particularly nitrogen, cooked inside the star's nuclear furnace and dredged up onto the stellar surface. The Chandra observations also show that the inner optical nebula glows faintly due to X-ray reflection. The X-rays reflected by the optical nebula come from very close to the star itself; these X-rays are generated by the high-speed collision of wind flowing from Eta Carinae's surface (moving at about 1 million miles per hour) with the wind of the companion star (which is about five times faster).

The companion is not directly visible in these images, but variability in X-rays in the regions close to the star signals the star's presence. Astronomers don't know exactly what role the companion has played in the evolution of Eta Carinae, or what role it will play in its future.


Posted by: Brooke Source

Ready for NASA climate change, ozone mission in tropics

The NASA WB-57 plane will fly into clouds at 60,000 feet during the TC4 mission in Costa Rica, sampling cloud particles and chemistry.

A high-flying NASA mission over Costa Rica and Panama in July and August should help researchers better understand how tropical storms influence global warming and stratospheric ozone depletion, says a University of Colorado at Boulder professor who is one of two mission researchers for the massive field campaign.

Brian Toon, chair of CU-Boulder's atmospheric and oceanic sciences department, said the $12 million effort will mobilize in San Jose, Costa Rica, and involve about 400 scientists, students and support staff operating three NASA aircraft, seven satellites and a suite of other instruments. The team is targeting the gases and particles that flow out of the top of the vigorous storm systems that form over the warm tropical ocean, said Toon.

The warm summer waters of the Pacific Ocean in Central and South America are a breeding ground for heat-driven convective storms targeted by the mission, said NASA officials. Such tropical systems are the major mechanism for Earth's system to loft air into the upper troposphere and stratosphere and are characterized primarily by cumulus clouds with large dense anvils and wispy cirrus clouds.

Known as the Tropical Composition, Cloud and Climate Coupling mission, or TC4, The expedition runs from July 16 through Aug. 8 and is NASA's largest field campaign in several years. The tropical storm systems under study pump air more than 40,000 feet above the surface, where they can influence the make-up of the stratosphere, home of Earth's protective ozone layer.

"This is a very little-studied region of the atmosphere, but it is crucial to understanding global climate change and changes in stratospheric ozone," Toon said.

One mission goal is to understand how transport of chemical compounds - both natural and man-made - occurs from the surface to the lower stratosphere, which is roughly 10 miles in altitude. Another goal is to understand the properties of high-altitude clouds and how they impact Earth' s radiation budget, Toon said.

As a TC4 mission scientist, Toon will be coordinating daily flights of three NASA aircraft filled with scientific instruments that will collect data in concert with NASA satellites. The aircraft include the ER-2 -- NASA's modern version of the Air Force U2-S reconnaissance aircraft -- which can reach an altitude of 70,000 feet and which will fly above the clouds and act as a "surrogate satellite," he said.

The mission also includes a broad-winged WB-57 research plane that will fly into the cirrus clouds at 60,000 feet and sample cloud particles and the make-up of chemicals flowing from massive tropical storm systems. The third plane, a converted DC-8, will fly at about 35,000 feet to probe the region between Earth' s troposphere and stratosphere and sample cloud particles and air chemistry.

"The critical lever in greenhouse warming is water in the upper troposphere," said Toon. "Added water, or more extensive clouds as a result of global warming, would significantly amplify the greenhouse effect from human made pollutants such as carbon dioxide." On the other hand, more extensive convection due to rising sea-surface temperatures could lead to more precipitation and less cloud cover, acting to "retard" greenhouse warming, he said.

Toon and his graduate students will be studying the size and role of ice particles in clouds to better understand how Earth might respond to warming temperatures. "We'd really like to understand the processes that control water as it is going into the stratosphere, which should help improve climate models," he said.

Toon, who spent several years helping to design the NASA mission and chaired the committee that organized the effort, also will be working with CU-Boulder graduate student Charles Bardeen in San Jose on daily weather forecasts, which will help dictate when planes can safely sample in targeted atmospheric regions.

Other participants from CU's oceanic and atmospheric sciences department, or ATOC, include Associate Professor Linnea Avallone, who will work with graduate students to sample water condensed in clouds. Associate Professor Peter Pilewskie and his students will study reflected sunlight from bright clouds to better understand Earth's energy budget in relation to climate change, while Research Associate Frank Evans will study ice cloud properties using radiometry.

Researchers from CU-Boulder's Cooperative Institute for Research in Environmental Sciences -- a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration -- also will participate in the mission. CIRES and NOAA have 14 scientists involved in the TC4 mission from Boulder.

Observations from a suite of NASA satellites flying in formation, known as the "A-Train," will complement the aircraft measurements. The satellites will measure ozone, water vapor, carbon monoxide and map clouds, charting the aerosol particles inside that affect their formation.

"The potential economic repercussions of global warming are almost unimaginable," said Toon. "We could lose large fractions of entire states over the next century or so if there are significant increases in sea level. "This mission will help us understand Earth's systems and what happens when we modify the planet".

Toon said NASA has a made a huge investment in its satellite fleet over the years and in finally implementing the TC4 mission. "NASA has a commitment to better understand these complex issues," he said. "And our graduate students will probably be writing theses on data from the TC4 mission for the next decade".


Posted by: Tyler Source

Search for 'weird' life

A new report from the National Research Council, examines the search for life elsewhere in the universe and whether the fundamental requirements for life as we generally know it are the only ways phenomena recognized as "life" could be supported beyond our planet.

Whether "weird" life, as researchers sometimes refer to life with a different biochemical structure than life here, should be considered in the search for extraterrestrial life is looked at in the report.


Posted by: Brooke Source

The Planet, the Galaxy and the Laser

On the night of 21 July, ESO astronomer Yuri Beletsky took images of the night sky above Paranal, the 2600m high mountain in the Chilean Atacama Desert home to ESO's Very Large Telescope. The amazing images bear witness to the unique quality of the sky, revealing not only the Milky Way in all its splendour but also the planet Jupiter and the laser beam used at Yepun, one of the 8.2-m telescopes that make up this extraordinary facility.

"The images are not composite", emphasises Yuri Beletsky. "The camera was being tracked on the stars, which can be easily noticed if you look at the telescope domes on the image (they look a little fuzzy). The colour of the laser beam on the first image actually looks pretty close to what one can see on the sky with the unaided eye."

Most striking in the images is the wide band of stars called the Milky Way. Spanning more than 100 degrees in the first of these images, it shows the dust and stars that are part of our own Galaxy, a spiral galaxy containing about 100 billion stars.

In the middle of this image, two bright objects are also seen. The brighter of the two is the planet Jupiter. The other is the bright star Antares. Another bright star, Alpha Centauri, one of the closest stellar neighbours to the Sun, is visible at the middle-left edge of the image.

Three of the four domes that shelter the 8.2-m VLT's Unit Telescopes are visible on the first image. Streaming out of Yepun, Unit Telescope number 4, is the laser beam used to create an artificial star above Paranal, aiming directly at the centre of our own Galaxy.

At the time the pictures were taken, astronomers were indeed using the SINFONI instrument (see ESO 21/04) to study the Galactic Centre, having a close look at the supermassive black hole that lurks in there.

With so a number of stars visible from the exceptional site of Paranal, one may wonder why it is necessary to create another, artificial, star? The answer lies in the very sophisticated instruments that are used on ESO's VLT. Some of them, such as NACO and SINFONI, make use of adaptive optics, a technique that allows astronomers to overcome the blurring effect of the atmosphere. This means that astronomers obtain images almost as good as if the whole telescope was placed in space, above Earth's atmosphere.

Adaptive optics, however, requires a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it (see ESO 07/06 and 27/07).

Launching such a powerful laser from a telescope is state-of-the-art technology, whose set-up and operation is a continuous challenge. As seen from the images, this is, however, a technology that is now well mastered on Paranal.

The images were obtained with a digital camera and 10-mm optics, mounted on a small equatorial mount, and are each the result of a single 5 minute exposure.


Posted by: Brooke Source

Gaping "Hole" in the Sky Found, Experts Say

Mason Inman
for National Geographic News
August 24, 2007

There is a yawning gap of sky nearly a billion light-years across that contains no matter, a new study suggests.

But some researchers aren't buying it, in part because it would be a monumental surprise to find a void that large.

When seen on the scale of tens of millions of light-years, the universe has a foamy structure, with galaxies arranged as if on strings or sheets, with little matter in between them.

This arrangement applies to both visible matter that pumps out light, such as stars, and the mysterious dark matter, whose existence can be inferred only indirectly from how it holds galaxies together.

(Related: "'Cosmic Train Wreck' May Derail Theories of Dark Matter" [August 22, 2007].)

But at much larger scales, about 150 million light-years and beyond, researchers had expected the universe would be more uniform—so finding a void nearly a billion light-years across was a shock.

"Not only has no one ever found a void this big, but we never even expected to find one this size," said study lead author Lawrence Rudnick of the University of Minnesota in Minneapolis.

Rudnick and colleagues Shea Brown and Liliya Williams report their findings in a paper accepted for publication in the Astrophysical Journal.

Unusual Spot of Sky

The researchers began looking at this particular spot in the sky because it already showed a strange feature.

There the cosmic microwave background radiation—low-level light left over from the birth of our universe that bathes all of space—is especially dim.

This dark patch—where the sky appears "cooler"—is known as the "WMAP cold spot," named after the Wilkinson Microwave Anisotropy Probe satellite that mapped the radiation in 2003.

The cold spot was surprising, because background radiation is remarkably uniform across the whole sky, interrupted only by small bumps and dips.

So Rudnick looked across the sky at galaxies that emit radio waves. He also tracked what the radio signals were like in the region of the WMAP cold spot to find a reason for the radiation dip.

Possible explanations included that the dip is a holdover from the beginnings of the universe or that a cosmic cloud is soaking up the radiation before it could reach Earth. (Related: "Proof of Big Bang Seen by Space Probe, Scientists Say" [March 17, 2006].)

But Rudnick found that in this region of the sky, there are also far fewer sources of radio waves.

The research team interpreted this as a huge void empty of both regular and dark matter that's nearly a billion light-years across.

"Although our surprising results need independent confirmation, the slightly lower temperature of the [radiation] in this region appears to be caused by a huge hole devoid of nearly all matter," Rudnick said. This hole is estimated to be about six to ten billion light-years away from Earth.

Open to Interpretation?

But some other researchers aren't convinced by this interpretation.

"The claims ... are interesting and important if correct," said Margaret Geller of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "But the argument for such a large completely empty void in the universe is not thoroughly convincing.

"Even the smaller voids detected in a wide variety of surveys are not completely empty," Geller added. "It is also odd that there are no other solid indications of structures approaching this scale."

"For this surprising finding to be taken seriously, more objects of comparable size should be found, something that is certainly not to be expected according to the standard model [of cosmology]," said Pablo Fosalba of the Autonomous University of Barcelona in Spain.

Yet the debate could be resolved soon.

The Planck satellite, due to launch in 2008, will produce "very clean extragalactic maps that will greatly help in resolving this puzzle," Fosalba said.