Old NASA satellite Crashed

While North America appears to be off the hook, scientists are scrambling to pinpoint exactly where and when a dead NASA climate satellite will plummet back to Earth on Friday.

The 6-ton, bus-sized satellite is expected to break into more than a hundred pieces as it plunges through the atmosphere, most of it burning up.

But if you're hoping for a glimpse, the odds are slim. Most sightings occur by chance because the re-entry path can't be predicted early enough to alert people, said Canadian Ted Molczan, who tracks satellites for a hobby.

In all his years of monitoring, Molczan has witnessed only one tumble back to Earth — the 2004 return of a Russian communications satellite.

It "looked like a brilliant star with a long glowing tail," he said in an email.

The best guess so far is that the 20-year-old Upper Atmosphere Research Satellite will hit sometime Friday afternoon or early evening, Eastern time. The latest calculations indicate it will not be over the United States, Canada and Mexico during that time.

Until Thursday, every continent but Antarctic was a potential target. Predicting where and when the freefalling satellite will land is an imprecise science, but officials should be able to narrow it down a few hours ahead.

While most of the satellite pieces will disintegrate, 26 large metal chunks — the largest about 300 pounds — are expected to survive, hit and scatter somewhere on the planet. With nearly three-quarters of the world covered in water, chances are that it will be a splashdown.

If the re-entry is visible, "it'll look like a long-lived meteor," said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Since the dawn of the Space Age, no one has been injured by falling space debris. The only confirmed case of a person being hit by space junk was in 1997 when Lottie Williams of Tulsa, Okla., was grazed in the shoulder by a small bit of debris from a discarded piece of a Delta rocket.

The odds of someone somewhere on Earth getting struck by the NASA satellite are 1 in 3,200. But any one person's odds are astronomically lower — 1 in 21 trillion.
"You're way more likely to be hit by lightning" than by the satellite, McDowell said.

NASA has warned people not to touch any satellite part they might chance upon. There are no hazardous chemicals on board, but people can get hurt by sharp edges, the space agency said.

The U.S. tracks the roughly 22,000 pieces of satellites, rockets and other junk orbiting the Earth. Nowadays, the world is more eco-conscious about what it puts up in space. Modern satellites must be designed to disintegrate upon re-entry or have enough fuel to be nudged into a higher orbit or steered into the ocean.

The satellite was launched in 1991 aboard the space shuttle Discovery to study the ozone layer, and back then there was no such rule. NASA used up the remaining fuel to put it into a lower orbit in 2005, setting the stage for its uncontrolled return. It will be the biggest NASA spacecraft to fall uncontrolled from the sky in 32 years.

It's not unusual for space debris to dive back to Earth. NASA's Orbital Debris Program Office estimates that medium-sized junk falls back once a week. Debris the size of the satellite due back Friday occurs less frequently, about once a year.

Harvard's McDowell noted that two massive Russian rocket stages have plunged back this year with little notice.

Astronomers say a bit of science fiction is now reality. They've spotted a planet orbiting two suns.

The discovery was made by NASA's planet-hunting telescope Kepler. Scientists describe the find in Friday's issue of the journal Science.

They are calling the new planet Tatooine after the fictional body in the "Star Wars" films that boasts a double sunset.

The alien world, about the size of Saturn, is frigid and inhospitable. It orbits two stars 200 light-years from Earth.

Though there have been past hints of the existence of other planets that circled double stars, scientists said this is the first confirmation.

Kepler was launched in 2009 to find out how common other planets — especially Earth-like planets — are in the universe.

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Online:

http://www.nasa.gov/mission_pages/kepler/main/index.html

A pair of spacecraft rocketed toward the moon Saturday on the first mission dedicated to measuring lunar gravity and determining what's inside Earth's orbiting companion

NASA launched the near identical probes — named Grail-A and Grail-B — aboard a relatively small Delta II rocket to save money. It will take close to four months for the spacecraft to reach the moon, a long, roundabout journey compared with the zippy three-day trip of the Apollo astronauts four decades ago.

Grail-A popped off the upper stage of the rocket exactly as planned 1½ hours after liftoff, followed eight minutes later by Grail-B. Both releases were seen live on NASA TV thanks to an on-board rocket camera, and generated loud applause in Launch Control.

The spacecraft are traveling independently to the moon, with A arriving on New Year's Eve and B on New Year's Day.

Once they were safely on their way, Zuber announced a contest for schoolchildren to replace the "working-class names" of Grail-A and Grail-B.

"Grail, simply put, is a journey to the center of the moon," said Ed Weiler, head of NASA's science mission directorate, borrowing from the title of the Jules Verne science fiction classic, "Journey to the Center of the Earth."

The world has launched more than 100 missions to the moon since the Soviet Union's Luna probes in 1959. That includes NASA's six Apollo moon landings that put 12 men on the lunar surface.
NASA's Grail twins — each the size of a washing machine — won't land on the moon but will conduct their science survey from a polar lunar orbit.
Beginning in March, once the spacecraft are orbiting just 34 miles above the moon's surface, scientists will monitor the slight variations in distance between the two to map the moon's entire gravitational field. The measurements will continue through May.
"It will probe the interior of the moon and map its gravity field 100 to 1,000 times better than ever before. We will learn more about the interior of the moon with Grail than all previous lunar missions combined," Weiler said.
At the same time, four cameras on each spacecraft will offer schoolchildren the opportunity to order up whatever pictures of the moon they want. The educational effort, called MoonKAM, is spearheaded by Sally Ride, America's first spacewoman. As of Saturday, more than 1,100 schools had signed up.
The entire Grail mission costs $496 million.
Zuber, the mission's principal investigator and a planetary scientist at the Massachusetts Institute of Technology, said the precise lunar gravity measurements will help her and other planetary scientists better understand how the moon evolved over the past 4 billion years. The findings also should help identify the composition of the moon's core: whether it's made of solid iron or possibly titanium oxide.
Another puzzle that Grail may help solve, Zuber said, is whether Earth indeed had a smaller second moon. Last month, astronomers suggested the two moons collided and the little one glommed onto the big one, a possible explanation for how the lunar highlands came to be.
Knowing where the moon's gravity is stronger will enable the United States and other countries to better pinpoint landing locations for future explorers, whether robot or human. The gravity on the moon is uneven and about one-sixth Earth's pull.
"If you want to land right next to a particular outcrop (of rock), you're going to be able to do it," Zuber said. "There will be no reason to do another gravity experiment of the moon in any of our lifetimes."
Zuber said the Grail findings should eliminate cliffhangers like the Apollo 11 landing in 1969 by Neil Armstrong and Buzz Aldrin. They overshot their touchdown site in part because of the subtle gravity changes in the moon's surface below; they almost ran out of fuel before safely touching down on the Sea of Tranquility.
"It will be easier next time," Zuber promised.
For now, NASA has no plans to return astronauts to the moon, Earth's closest neighbor at approximately 240,000 miles away. That program, called Constellation, was canceled last year by President Barack Obama, who favors asteroids and Mars as potential destinations in America's future without the shuttle.
This is the second planetary mission for NASA since the space shuttle program ended in July, and attracted a large crowd to Cape Canaveral. NASA counted nearly 1,000 guests at Kennedy Space Center on Saturday, nowhere near the 12,000 on hand for the Juno launch to Jupiter at the beginning of August.
Grail was supposed to soar Thursday, but high wind interfered. Then NASA needed an extra day to check the rocket after engine heaters stayed on too long. High wind almost stopped NASA again Saturday; the launch team had to skip the morning's first opportunity, but the wind dissipated just in time for the second.
The year's grand finale will be the launch of the biggest Mars rover ever the day after Thanksgiving.
"NASA is still doing business even though the shuttles stopped flying," Weiler told reporters earlier in the week.
Grail is the 110th mission to target the moon, according to NASA records. Missions have been launched by the United States, Soviet Union, Japan, China and India.
The previous moonshot was two years ago: NASA's Lunar Reconnaissance Orbiter. Just last month, the moon-circling probe beamed back the sharpest pictures yet of some of the Apollo artifacts left on the moon from 1969 through 1972 — and even moonwalkers' tracks. NASA released the photos earlier in the week.
Ride and Zuber will help pick the winning names for the Grail twins later this year, well before the spacecraft reach the moon.

Zuber said she has her own pet names, "but I think I'll keep those to myself because I don't want to influence the contestants." Some of the names used by members of her team over the four-year life of the project: Fred and Ginger, Castor and Pollux, and Tom and Jerry.

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Online:
NASA: http://www.nasa.gov/mission_pages/grail/main/index.html

Sally Ride Science: http://moonkam.ucsd.edu/

Four decades after landing men on the moon, NASA is returning to Earth's orbiting companion, this time with a set of robotic twins that will measure lunar gravity while chasing one another in circles

By creating the most precise lunar gravity map ever, scientists hope to figure out what's beneath the lunar surface, all the way to the core. The orbiting probes also will help pinpoint the best landing sites for future explorers, whether human or mechanical.

Near-identical twins Grail-A and Grail-B — short for Gravity Recovery and Interior Laboratory — are due to blast off Thursday aboard an unmanned rocket.

Although launched together, the two washing machine-size spacecraft will separate an hour into the flight and travel independently to the moon.

It will be a long, roundabout trip — three to four months — because of the small Delta II rocket used to boost the spacecraft. NASA's Apollo astronauts used the mighty Saturn V rocket, which covered the approximately 240,000 miles to the moon in a mere three days.

NASA's Grail twins will travel more than 2 million miles to get to the moon under this slower but more economical plan.

The mission, from start to finish, costs $496 million.

The moon's appeal is universal.

"Nearly every human who's every lived has looked up at the moon and admired it," said Massachusetts Institute of Technology planetary scientist Maria Zuber, Grail's principal investigator. "The moon has played a really central role in the human imagination and the human psyche."

Since the Space Age began in 1957, 109 missions have targeted the moon, 12 men have walked its surface during six landings, and 842 pounds of rock and soil have been brought back to Earth and are still being analyzed.

Three spacecraft currently are orbiting the moon and making science observations. A plan to return astronauts to the moon was nixed in favor of an asteroid and Mars.

Despite all the exploration, scientists still don't know everything about the moon, Zuber noted. For example, its formation still generates questions — Grail's findings should help explain its origin — and its far side is still mysterious.

"You would think having sent many missions to the moon we would understand the difference between the near side and the far side, but in fact we don't," she said.

Recent research suggests Earth may have had a second smaller moon that collided with our present moon, producing a mountainous region. The Grail mission may help flush out that theory, Zuber said.

Grail-A will arrive at the moon on New Year's Eve, followed by Grail-B on New Year's Day. They will go into orbit around the lunar poles and eventually wind up circling just 34 miles above the surface.

For nearly three months, the spacecraft will chase one another around the moon, meticulously flying in formation. The distance between the two probes will range from 40 miles to 140 miles. Radio signals bouncing between the twins will provide their exact locations, even on the far side of the moon.

Scientists will be able to measure even the slightest variations in the gap between orbiting Grail-A and Grail-B — every single second. These subtle changes will indicate shifting masses below or at the lunar surface: mountains in some places, enormous lava tubes and craters in others.

The moon actually has the most uneven gravitational field in the solar system, according to NASA. The moon's gravity is about one-sixth Earth's pull.

"We measure the velocity change between the two spacecraft to a couple of fractions of a tenth of a micron per second. It is an extremely accurate measurement that has to be made," Zuber said.

A tenth of a micron is about half the size of a red blood cell.

By the time their science mission ends in late spring, Grail-A and Grail-B will be within 10 miles of the lunar surface. Barring a change in plans, they will crash into the moon.

Each spacecraft holds one science instrument— for sending and receiving radio signals between the two — as well as a digital video camera system, MoonKAM, intended for use by middle school students worldwide. Sally Ride, the first American woman in space, and her science education company in San Diego is leading the photo-gathering effort. It's billed as "eyes on the moon for Earth's students."

This is NASA's second robotic mission to be launched since the end of the shuttle program in July. A probe named Juno is headed for Jupiter following an Aug. 5 liftoff.

NASA officials will be thrilled if Grail generates even a portion of the immense interest ignited by the Juno launch. A large crowd is expected at Cape Canaveral for Thursday's morning liftoff, which features a pair of split-second launch windows a half-hour apart.

"We're just delighted by the way the country is responding to these exciting missions," said Jim Green, director of NASA's planetary science division.

Astronauts may need to take the unprecedented step of temporarily abandoning the International Space Station if last week's Russian launch accident prevents new crews from flying there this fall.

Until officials figure out what went wrong with Russia's essential Soyuz rockets, there will be no way to launch any more astronauts before the current residents have to leave in mid-November.

The unsettling predicament comes just weeks after NASA's final space shuttle flight.

"We have plenty of options," NASA's space station program manager, Mike Suffredini, assured reporters Monday. "We'll focus on crew safety as we always do."

Abandoning the space station, even for a short period, would be an unpleasant last resort for the world's five space agencies that have spent decades working on the project. Astronauts have been living aboard the space station since 2000, and the goal is to keep it going until 2020.

Suffredini said flight controllers could keep a deserted space station operating indefinitely, as long as all major systems are working properly. The risk to the station goes up, however, if no one is on board to fix equipment breakdowns.

Six astronauts from three countries presently are living on the orbiting complex. Three are due to leave next month; the other three are supposed to check out in mid-November. They can't stay any longer because of spacecraft and landing restrictions.

The Sept. 22 launch of the very next crew — the first to fly in this post-shuttle era — already has been delayed indefinitely. Russia's Soyuz spacecraft have been the sole means of getting full-time station residents up and down for two years. The capsule is parked at the station until they ride it home.

To keep the orbiting outpost with a full staff of six for as long as possible, the one American and two Russians due to return to Earth on Sept. 8 will remain on board at least an extra week.

As for supplies, the space station is well stocked and could go until next summer, Suffredini said. Atlantis dropped off a year's supply of goods just last month on the final space shuttle voyage. The unmanned craft destroyed Wednesday was carrying 3 tons of supplies.

For now, operations are normal in orbit, Suffredini noted, and the additional week on board for half the crew will mean additional science research.

The Soyuz has been extremely reliable over the decades; this was the first failure in 44 Russian supply hauls for the space station. Even with such a good track record, many in and outside NASA were concerned about retiring the space shuttles before a replacement was ready to fly astronauts.

Russian space officials have set up an investigation team and until it comes up with a cause for the accident and a repair plan, the launch and landing schedules remain in question. None of the spacecraft debris has been recovered yet; the wreckage fell into a remote, wooded section of Siberia. The third stage malfunctioned; a sudden loss of pressure apparently was noted between the engine and turbopump.

While a crew may well have survived such an accident because of safety precautions built into the manned version of the rocket, no one wants to take any chances.

One or two unmanned Soyuz launches are on tap for October, one commercial and the other another space station supply run. Those would serve as important test flights before putting humans on board, Suffredini said.

NASA considered vacating the space station before, following the space shuttle Columbia disaster in 2003. Back then, shuttles were still being used to ferry some station residents back and forth. Instead, the station got by with two-man crews for three years because of the significant cutback in supplies.

The space station's population doubled in 2009, to six. It wasn't until the space station was completed this year that science research finally took priority.

Even if the space shuttles still were flying, space station crews still would need Soyuz-launched capsules to serve as lifeboats, Suffredini said. The capsules are certified for no more than 6½ months in space, thus the need to regularly rotate crews. Complicating matters is the need to land the capsules during daylight hours in Kazakhstan, resulting in weeks of blackout periods.

NASA wants American private companies to take over crew hauls, but that's three to five years away at best. Until then, Soyuz capsules are the only means of transporting astronauts to the space station.

Japan and Europe have their own cargo ships and rockets, for unmanned use only. Commercial front-runner Space Exploration Technologies Corp., or SpaceX, plans to launch a space station supply ship from Cape Canaveral at the end of November. That would be put on hold if no one is on board to receive the vessel.

Suffredini said he hasn't had time to consider the PR impact of abandoning the space station, especially coming so soon after the end of the 30-year shuttle program.

"Flying safely is much, much more important than anything else I can think about right this instant," he said. "I'm sure we'll have an opportunity to discuss any political implications if we spend a lot of time on the ground. But you know, we'll just have to deal with them because we're going to do what's safest for the crew and for the space station."

Ancient humans fashioned hand axes, cleavers and picks much earlier than believed, but didn't take the stone tools along when they left Africa, new research suggests.

A team from the United States and France made the findings after traveling to an archaeological site along the northwest shoreline of Kenya's Lake Turkana. Two-faced blades and other large cutting tools had been previously excavated there along with primitive stone flakes.

Using a sophisticated technique to date the dirt, researchers calculated the age of the more advanced tools to be 1.76 million years old. That's older than similar stone-age artifacts in Ethiopia and Tanzania estimated to be between 1.4 and 1.6 million years old.

This suggests that prehistoric humans were involved in refined tool-making that required a higher level of thinking much earlier than thought. Unlike the simplest stone tools made from bashing rocks together, the early humans who shaped these more distinct objects planned the design and then created them.

This "required a good deal of forethought as well as dexterity to manufacture," said paleoanthropologist Eric Delson at Lehman College in New York, who was not involved in the research.

Results of the study, led by Christopher Lepre of Rutgers University and Columbia University's Lamont-Doherty Earth Observatory, appear in Thursday's issue of the journal Nature.

The stone tools, known collectively as Acheulian tools, are believed to be the handiwork of the human ancestor Homo erectus. The teardrop-shaped axes were "like a stone-age Leatherman or Swiss Army knife," said New York University anthropologist Christian Tryon.

The axes were suited for butchering animals or chopping wood while the thicker picks were used for digging holes.

Homo erectus walked upright like modern humans, but possessed a flat skull, sloping forehead and a smaller brain. It emerged about 2 million years ago in Africa. Most researchers think Homo erectus was the first to fan out widely from Africa.

There's archaeological evidence that the first to leave carried only a simple toolkit. The earliest sites recovered in Asia and Europe contain pebble tools and flakes, but no sign of Acheulian technology like hand axes.

Why that is "remains an open question," said anthropologist Sally McBrearty of the University of Connecticut, who had no role in the research.

Theories abound. Some surmise that the early humans could not find the raw materials in their new settlement and lost the technology along the way. Others suggest they later returned to Africa where they developed hand axes.

NYU's Tryon, who was not part of the study, has a different thought. Perhaps the early populations who expanded out of Africa didn't need advanced technology because there was less competition.

Early humans were "behaviorally flexible" and making hand axes "was something that they did as needed and abandoned when not needed," Tryon said.

The latest work does little to settle the issue, but scientists now have identified the earliest known site in the world containing Acheulian tools.

Geologists collected about 150 samples of sediment from the site in 2007. To come up with an age, they used a technique known as paleomagnetic dating, which takes advantage of the flip-flop of Earth's magnetic field every several hundred thousand years.

The tools were not too far from where the bones of Turkana Boy — the most complete skeleton of a prehistoric human — were unearthed in 1984.

A newly discovered alien planet that formed from a dead star is a real diamond in the rough.

The super-high pressure of the planet, which orbits a rapidly pulsing neutron star, has likely caused the carbon within it to crystallize into an actual diamond, a new study suggests.

The composition of the planet, which is about five times the size of Earth, is not its only outstanding feature. [Illustration of the diamond alien planet]

The planet's parent star is a special kind of flashing star known as a millisecond pulsar, a rapidly rotating neutron star formed from a supernova. The entire system, which is only the second of its kind ever discovered, is located about 4,000 light-years from Earth in the constellation of Serpens (The Snake).

A gem of a find

Seventy percent of millisecond pulsars found have a companion, which provides additional energy to ramp up the pulsars' rapid rotation. Generally, this companion is a dying star called a white dwarf; more than 180 millisecond pulsars have been found with white dwarfs over the years.

Theonly planet known to be orbiting in such a system was detected in 1992 — until now."The pulsar was found in December 2009," lead scientist Matthew Bailes of Swinburne University of Technology in Melbourne, Australia, told SPACE.com via email."We've been on the trail of the companion ever since." [The Strangest Alien Planets]

From the ashes of a supernova

Known as PSR J1719-1438, this particular pulsar completes more than 10,000 rotations in a minute. Tiny and compact, it's only about 12 miles (20 kilometers) across, but it has a mass that is 1.4 times that of our sun.

PSR J1719-1438 transformed from an average star to a radio pulsar when a dying star in a binary system exploded. The compact core of the star formed with a very high rotation speed from the ashes of the supernova.

When the second star in the system reached the end of its life, it expanded as a red giant and finally morphed into a white dwarf. The pulsar began to suck mass off its companion, causing the pulsarto spin faster and faster until it attained its breakneck speed.

From dying star to diamond planet

What happened next depends on the system. Most white dwarfs continue to orbit the new millisecond pulsar, but some are consumed by it.

"The fate depends upon the mass of the white dwarf and how far it is from the pulsar," Bailes said.

If it is both close and massive, the two spiral together. Astronomers assume this is what happened to the 30 percent of millisecond pulsars found without a companion. [Top 10 Star Mysteries]

In the case of the diamond planet, astronomers think that the core of the white dwarf failed to merge completely with its companion.

"When they got very close, the star lost a lot of its matter and moved out to its safe distance of about a solar radius," Bailes said.

Now tiny, having lost more than 99.9 percent of its original mass and no longer engaged in the fusion reactions that drive a star, the dead core is classified as a planet.

Ironically, the star-turned-planet is larger than its sun. With a diameter of about 37,300 miles (60,000 km), it's five times the size of Earth, but 3,000 times larger than the millisecond pulsar it orbits.

The planet itself orbits the pulsar in a little more than two hours. The entire system would fit within the diameter of our sun.

The research was published online in the Aug. 25 edition of the journal Science.

Visit SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcomand onFacebook.

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NASA's humanoid robot has finally awakened in space.

Ground controllers turned Robonaut on Monday for the first time since it was delivered to the International Space Station in February. The test involved sending power to all of Robonaut's systems. The robot was not commanded to move; that will happen next week.

"Those electrons feel GOOD! One small step for man, one giant leap for tinman kind," Robonaut posted in a Twitter update. (All right, so a Robonaut team member actually posted Monday's tweets under AstroRobonaut.)

The four visible light cameras that serve as Robonaut's eyes turned on in the gold-colored head, as did the infrared camera, located in the robot's mouth and needed for depth perception. One of Robonaut's tweets showed the view inside the American lab, Destiny.

"Sure wish I could move my head and look around," Robonaut said in the tweet.

Robonaut — the first humanoid robot in space — is being tested as a possible astronaut's helper.

The robot's handlers at Mission Control in Houston cheered as everything came alive. The main computers — buried inside Robonaut's stomach — kicked on, as did the more than 30 processors embedded in the arms for controlling the joints.

"Robonaut behaved himself," said deputy project manager Nicolaus Radford. "Oh, Robonaut definitely got an 'A.' He won't be held back a grade, if that's what you want to know."

"It was just very exciting," he said. "It's been a long time coming to get this thing turned on."

The robot was delivered on space shuttle Discovery's final flight. It took this long for the operating software to get up there, and for the astronauts to have enough time to help with the experiment

On Sept. 1, controllers will command Robonaut to move its fingers, hands and arms.

"It's been asleep for about a year, so it kind of has to stretch out a little bit," Radford told The Associated Press. "Just like a crew member has to kind of acclimate themselves to zerogravity, our robot has to do a very similar thing, kind of wiggle itself and learn how it needs to move" in weightlessness.

For now, Robonaut exists from the waist up. It measures 3 feet 4 inches tall and weighs 330 pounds. Each arm is 2 feet 8 inches long.

A pair of legs currently are being designed and should be launched in 2013.

Radford said if everything continues to check out well, the robot may be able to take on a few mundane chores — like taking air velocity measurements inside the space station — early next year.

For now, Robonaut — also called R2 — is designed to stay inside the space station. Future versions might venture out on spacewalks, saving astronauts time while keeping them safe.

During Monday's two-hour test, U.S. astronaut Michael Fossum and Japanese spaceman Satoshi Furukawa took Robonaut from its sleeping bag, placed it on its fixed pedestal, then floated away as ground controllers took over. The robot went back into its bag following the test.

Because Robonaut has some flammable parts, NASA wants it stored in its fireproof bag.

Controllers were tempted to make the robot move, but held off.

"We want to be respectful," Radford said. "It's a very complicated piece of hardware."

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Online:

NASA: http://robonaut.jsc.nasa.gov/default.asp

Scientists have found Earth's oldest fossils in Australia and say their microscopic discovery is convincing evidence that cells and bacteria were able to thrive in an oxygen-free world more than 3.4 billion years ago.

The finding suggests early life was sulphur-based -- living off and metabolizing sulphur rather than oxygen for energy -- and supports the idea that similar life forms could exist on other planets where oxygen levels are low or non-existent.

"Could these sorts of things exist on Mars? It's just about conceivable. This evidence is certainly encouraging and lack of oxygen on Mars is not a problem," said Martin Brasier of Oxford University, who worked on the team that made the discovery.

The microfossils, which the researchers say are very clearly preserved and show precise cell-like structures, were found in a remote part of western Australia called Strelley Pool.

In a study published in the journal Nature Geoscience on Sunday, Brasier's team explained that the tiny fossils were preserved between the quartz sand grains of the oldest shoreline known on Earth in some of the oldest sedimentary rocks ever discovered.

"We can be very sure about the age as the rocks were formed between two volcanic successions that narrow the possible age down to a few tens of millions of years," he said. "That's very accurate indeed when the rocks are 3.4 billion years old."

By analyzing the fossils, the rocks they were found in and the surrounding environment, the scientists have built a picture of Earth at this time as a hot, murky, violent place where there was a high and constant threat of volcanic eruptions and meteor strikes.

The sky would have been cloudy and grey, keeping the heat in even though the sun would have been weaker than today, and the oceans would have been around 40-50 degrees Celsius -- the temperature of a hot bath.

Most significantly, there was very little oxygen around since there were no plants or algae to photosynthesize and produce it, Brasier explained in a telephone interview.

"It's a rather hellish picture," he said. "Not a great place for the likes of us. But for bacteria, all of this was wonderful. In fact, if you were to invent a place where you wanted life to emerge, the early Earth is exactly right."

The researchers are now using the techniques and approaches they used in this study to re-examine other fossil finds that scientists have suggested may also contain evidence for very early life on Earth.

In a laboratory in the center of Manhattan scientists continue to struggle to put names to the remains of victims from the September 11, 2001 attacks, some 40 percent of which are still unidentified

"It's not a legal obligation because everybody has a death certificate. It's an ethical-moral decision," said Mechthild Prinz in the department of forensic biology at the city's Chief Medical Examiner office.

The names of the people who died in the explosions, fires and collapse in the Twin Towers on 9/11 are known, but the violence was so extreme that even a decade later it takes painstaking forensic work to match those identities to the human fragments found at the site.

The latest match made was just this week: Ernest James, who was 40 years old. He was the 1,629th victim identified out of 2,753 people killed at the World Trade Center, or 59 percent of the total.

Initially, traditional methods such as dental records, photographs and finger prints were used to identify the bodies and remains pulled from the rubble. But as the easier batches of remains were dealt with the gruesome task turned into something more akin to serious detective work -- and even that is not enough in many cases.

"We did collect 21,817 remains, so you can imagine obviously that a lot of people were fragmented in many different body parts. And since we haven't identified over a thousand people, some of them really disappeared," said Prinz, 53, who comes from Germany but has been working as a forensic scientist in New York since 1995.

Amid strict security and sanitation conditions, a team of five scientists continues to deal with 6,314 fragments of bones found in the World Trade Center area.

An AFP journalist was shown the work underway through a window in a door before being told to put on gloves and taken into a large room, where robots clean the remains before they are tested for DNA against a databank created by relatives of the deceased.

"I remember a case a few years ago which was a small piece of bone on the roof of the Deutsche Bank building. It was the size of a coin and we were able to identify someone who worked in the towers at that time," recalled Taylor Dickerson, a criminalist in the forensic biology department.

However in most cases the DNA found in the fragments turns out to be just another piece of a person already identified. As a result, the work is painfully slow: fewer than three dozen people have been identified since 2006.

Sometimes, DNA is found in bone fragments that cannot be matched to anyone in the databank -- either because relatives did not give samples or because the remains belong to an illegal immigrant who happened to be in the area at the time and was never registered.

Prinz said the work, for all its frustrations, is satisfying.

"It definitely was worthwhile to do it, because some of the families are really grateful," he said.

"I guess the biggest thing for me has been just understanding the impact our work has on both the families and the community, the forensic community," Dickerson said. "I never expected to do that in my career."

Our world is a much wilder place than it looks. A new study estimates that Earth has almost 8.8 million species, but we've only discovered about a quarter of them

So far, only 1.9 million species have been found. Recent discoveries have been small and weird: a psychedelic frogfish, a lizard the size of a dime and even a blind hairy mini-lobster at the bottom of the ocean.

Click photo to view more images. (AP/NOAA)

"We are really fairly ignorant of the complexity and colorfulness of this amazing planet," said the study's co-author, Boris Worm, a biology professor at Canada's Dalhousie University. "We need to expose more people to those wonders. It really makes you feel differently about this place we inhabit."

While some scientists and others may question why we need to know the number of species, others say it's important.

There are potential benefits from these undiscovered species, which need to be found before they disappear from the planet, said famed Harvard biologist Edward O. Wilson, who was not part of this study. Some of modern medicine comes from unusual plants and animals.

"We won't know the benefits to humanity (from these species), which potentially are enormous," the Pulitzer Prize-winning Wilson said. "If we're going to advance medical science, we need to know what's in the environment."

Biologists have long known that there's more to Earth than it seems, estimating the number of species to be somewhere between 3 million and 100 million. Figuring out how much is difficult.

Worm and Camilo Mora of the University of Hawaii used complex mathematical models and the pace of discoveries of not only species, but of higher classifications such as family to come up with their estimate.

Their study, published Tuesday in the online journal PLoS Biology, a publication of the Public Library of Science, estimated the number of species at nearly 8.8 million.

Of those species, 6.5 million would be on land and 2.2 million in the ocean, which is a priority for the scientists doing the work since they are part of the Census of Marine Life, an international group of scientists trying to record all the life in the ocean.

The research estimates that animals rule with 7.8 million species, followed by fungi with 611,000 and plants with just shy of 300,000 species.

While some new species like the strange mini-lobster are in exotic places such as undersea vents, "many of these species that remain to be discovered can be found literally in our own backyards," Mora said.

Outside scientists, such as Wilson and preeminent conservation biologist Stuart Pimm of Duke University, praised the study, although some said even the 8.8 million number may be too low.

The study said it could be off by about 1.3 million species, with the number somewhere between 7.5 million and 10.1 million. But evolutionary biologist Blair Hedges of Penn State University said he thinks the study is not good enough to be even that exact and could be wrong by millions.

Hedges knows firsthand about small species.

He found the world's smallest lizard, a half-inch long Caribbean gecko, while crawling on his hands and knees among dead leaves in the Dominican Republic in 2001. And three years ago in Barbados, he found the world's shortest snake, the 4-inch Caribbean threadsnake that lays "a single, very long egg."

The study's authors point to other species as evidence of the growing rate of discovery: the 6-inch, blind, hairy lobster-type species found in 2005 by a submarine looking at hydrothermal vents near where the Pacific meets Antarctica and a brilliant-colored frogfish found by divers in Indonesia in 2008.

Of the 1.9 million species found thus far, only about 1.2 million have been listed in the fledgling online Encyclopedia of Life, a massive international effort to chronicle every species that involves biologists, including Wilson.

If the 8.8 million estimate is correct, "those are brutal numbers," said Encyclopedia of Life executive director Erick Mata. "We could spend the next 400 or 500 years trying to document the species that actually inhabit our planet."