Tag Archives: space

Keys to life? Scientists explain how newly-discovered exoplanets could be habitable

About 40 light years from Earth, there is an intriguing system with a dim red star and seven alien worlds rapidly orbiting it.

And what makes the find so exciting is that three of those planets are in the “Goldilocks zone” of the star: the just-right place where liquid water could exist on a planet’s rocky surface.

The announcement of the discovery around the star called TRAPPIST-1, made yesterday by NASA, is a reminder of the ultimate question: is there life in the universe besides what we know of on Earth?

And could any of these TRAPPIST-1 planets— especially the three in the habitable zone— have the right ingredients for it to develop?

“The news is wonderful, and has been since last year, when the first three planets in this system were discovered,” Dimitar Sasselov, a professor of astronomy at Harvard University, and a researcher who focuses on studying the origins of life in his lab, told Fox News. “This just confirms what we started theorizing already in the past two years: [which] is that our galaxy, our universe, is just full of places which could sustain life, and where life could emerge.”

Part of the reason the news is wonderful is that the system lends itself to being studied by astronomers in the next couple years— and not way down the line— Sasselov said. The three planets in the habitable zone of this star are promising because their rocky surfaces could support liquid water, which is essential for life as we know it.

Plus, if the planets are indeed rocky, they could contain the six right elements in the right concentration for life, Sasselov said: stuff like carbon, oxygen, and nitrogen.

David Kipping, an expert on exoplanets and an assistant professor of astronomy at Columbia University, said that his first reaction to the discovery was to be “extremely excited.”

The star that the seven planets are orbiting is a very common one called a red dwarf— it’s small, dim, and cool compared to our own sun, but it could also burn for a very, very long time: somewhere on the order of a trillion years, or even longer, Kipping said.

“When we look for potentially life-bearing planets, there’s really one thing we’re looking for, and that’s liquid surface water,” Kipping told Fox News. Of course, in order to have surface water, the planet needs to have a rocky surface, and he said that the planets seem likely to have that. Another point in their favor? There are three planets in the system that would be at the right temperature for liquid water to exist.

“That doesn’t prove they’re definitely capable of supporting of life,” he said. After all, one or two of the three planets could be like Venus in our solar system, which has nasty conditions. But still, three planets is better than two or one, odds-wise. “With three bites at the cherry, you have to be optimistic that there’s a good shot one of them has the potential to be Earth-like.”

He added: “As far as we know right now, I’d say there are no show-stoppers to stop life from living on these worlds.”

There are a couple factors to consider, though. Astronomers will have to study the star further (it could have emitted a lot of radiation when it was young, for example), as well as the masses of the planets and the shape of their orbits (to see how elliptical they are) to figure out how conducive they could be for life. The next step, Kipping said, will be to look for biosignatures on the planets using a telescope. (The James Webb Space Telescope, launching in 2018, will be an important resource for astronomers.)

Lisa Kaltenegger, as associate professor of astronomy, and the director of the Carl Sagan Institute at Cornell University, said that one aspect to consider with this “small red sun” is that the levels of ultraviolet light could be high, although life could perhaps shelter in a hypothetical ocean.

“I think finding many planets, multiple possible habitats, around one star is great news for the search for life,” she said, pointing out that the news made her feel motivated. “Because that just means we’re getting more places to look. And it’s just a numbers game— we already have a lot of stars with planets, now if we have a couple of planets per star, the odds are ever in our favor, hopefully.”

Follow Rob Verger on Twitter: @robverger

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Mars meteorite 1st look at Red Planet’s ancient crust

Sawn surface of the Mars meteorite NWA 7533 showing both light and dark clasts in grey matrix.

Sawn surface of the Mars meteorite NWA 7533 showing both light and dark clasts in grey matrix. (Luc Labenne)

A meteorite found last year in the Sahara Desert is likely the first recognized piece of ancient Martian crust, a new study reports.

The Mars meteorite NWA 7533 is 4.4 billion years old and contains evidence of long-ago asteroid strikes, suggesting that the rock came from the Red Planet’s ancient and cratered southern highlands, researchers said.

“We finally have a sample of the Martian highlands, that portion of Mars that holds all the secrets to Mars’ birth and early development,” lead author Munir Humayun of Florida State University told SPACE.com via email. [Photos: Amazing Meteorites from Mars]

“It’s the part of Mars’ history where the oceans and atmosphere developed, and where life would have developed if it ever did on Mars,” Humayun added. “I will liken this to opening a treasure chest — it may take a while before we find the best treasures, but treasures aplenty lurk in this meteorite.”

Humayun and his colleagues subjected NWA (short for northwest Africa, where the rock was found) 7533 to a series of analyses. The researchers determined the meteorite’s age, for example, by determining that crystals within it called zircons formed about 4.4 billion years ago.

“This date is about 100 million years after the first dust condensed in the solar system,” Humayun said in a statement. “We now know that Mars had a crust within the first 100 million years of the start of planet-building, and that Mars’ crust formed concurrently with the oldest crusts on Earth and the moon.”

The team also found high concentrations of normally rare elements such as nickel, osmium and iridium in NWA 7533, indicating that the rock formed in a region that was pummeled by chondritic meteors, which are relatively enriched in these materials.

Further, after measuring the abundances of certain elements within the meteorite, Humayun and his team were able to calculate a thickness for the Red Planet’s crust.

“The amount of melting on Mars was low, sufficient to accumulate a 50-kilometer-thickness [31 miles] crust, but Mars evidently escaped the giant impact-style melting that affected the Earth and moon,” Humayun told SPACE.com. (Most scientists think the moon formed from material blasted into space when a planet-size body crashed into Earth more than 4 billion years ago.)

“This is the first reliable geochemical estimate of the thickness of Mars’ crust, and it agrees with geophysical estimates from gravity and topography,” he added.

Though researchers believe ancient Mars was relatively warm and wet, the team found no hydrous silicate minerals — which form in the presence of liquid water — within NWA 7533. Scientists will likely unearth more such puzzling details as they study the meteorite further, Humayun said.

“I expect more surprises as we dig deeper into our Martian treasure chest — some we will understand, and others may continue to befuddle us for a while to come,” he said.

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Glass Invented for Drinking Whiskey in Space – Finally!

A Special Whisky Glass for Special Space Whisky

If Galactic’s first commercial flights are any indication, life in space could use a bit more glamour. Astronauts may be fine drinking recycled pee, but celebrities and wealthy space enthusiasts, who have spent hundreds of thousands of dollars to get beyond Earth’s atmosphere, may want to sip something a little stronger. Enter Scotch-maker Ballantine’s new space glass, designed for drinking in microgravity.

Without Earth’s gravity, a regular snifter would send droplets of fancy Scotch soaring into the air—and away from mouths. The Ballantine’s glass is designed to keep the whisky where it belongs. A metal plate at the bottom of the glass creates surface tension to keep the Scotch—poured into the bottom of the cupcontained. Rivulets running up the side of the glass channel the liquid directly into the mouth via a gold mouthpiece. (The company details the design process here.)

Scotch whisky companies seem particularly determined to corner the space drinking market. Ardberg whisky, for instance, is already an old pro at intergalactic refreshments, as vials of the Scotch spent several years on the International Space Station before returning last year. (The verdict: space makes smoky Scotch even smokier.) Several breweries also offer beer made from yeast that’s left Earth and returned, in case hard liquor isn’t your cup of astro-tea.

Naturally, those of us who are earthbound can still buy Ballantine’s space glass for an out-of-this-world experience.

[h/t: The New York Times]

All images by Ballantine’s via Medium

September 8, 2015 – 5:00pm

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New ESA chief proposes building a full-fledged human village on the moon

There’s a new head of the European Space Agency, and after just two weeks on the job, he’s bringing some ambitious ideas to the table. First up: A human village on the moon.

In an interview with the BBC, new ESA head Johann-Dietrich Woerner chatted about the priorities for the agency in the coming years — and dropped a really big one currently on his wish list. According to Woerner, it’s all about testing out this technology before we actually try to ship humans off to somewhere like Mars. So, his idea is to have several nations team up for a legitimate settlement on the moon, so we can work out all the kinks to man an eventual Mars trip less of a suicide mission.

Here’s an excerpt from his comments:

“We should look to the future beyond the International Space Station. We should look for a smaller spacecraft in low-Earth orbit for microgravity research and I propose a Moon village on the far side of the Moon.

A Moon village shouldn’t just mean some houses, a church and a town hall. This Moon village should mean partners from all over the world contributing to this community with robotic and astronaut missions and support communication satellites.”

This is an awesome idea, to say the least, though we should obviously caution that it’s currently a pipe dream. The amount of money and time needed to pull this off would be incredible, and right now it’s just a spitball idea. But regardless, it’s nice to know the idea is at least on the whiteboard.

What do you think? Mars first, or a lunar village?

(Via BBC, io9)

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Space station shipment launched from Virginia

Space station shipment launched from Virginia

Orbital Sciences Corp. launched its Cygnus capsule from the Virginia coast, its third space station delivery for NASA.

Daylight and clouds limited visibility, but observers from North Carolina to New Jersey still had a shot at seeing the rising Antares rocket. It resembled a bright light in the early afternoon sky.
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Its destination, the space station, was soaring 260 miles above Australia when the Cygnus took flight. The unmanned capsule should arrive there Wednesday.

This newest Cygnus contains more than 3,000 pounds of supplies, much of it food. Also on board: mini-satellites, science samples, equipment and experimental exercise clothes. NASA said the new type of clothing is resistant to bacteria and odor buildup. So the astronauts won’t smell as much during their two hours of daily workout in orbit and they’ll require fewer clothing changes.

NASA is paying for the delivery service. The space agency hired two companies — the Virginia-based Orbital Sciences and California’s SpaceX — to keep the space station well stocked once the shuttle program ended. The international partners also make shipments; the European Space Agency, for example, will launch its supply ship in 1 1/2 weeks from French Guiana.

This particular Cygnus delivery was delayed a few months by various problems, including additional engine inspections and, most recently, bad weather at the Wallops Island launch site.

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The Cygnus will remain at the space station for about a month. It will be filled with trash and cut loose for a fiery re-entry. Unlike the SpaceX Dragon capsule, the Cygnus is not built to return safely to Earth.

Saturday, meanwhile, marked the 5,000th day of continuous human habitation at the 260-mile-high outpost. Six men currently are on board, representing the United States, Russia and Germany.

“Humans are explorers!” German astronaut Alexander Gerst said via Twitter.

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Mars ‘flying saucer’ splashes down after NASA test

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FILE – In this undated file photo provided by NASA, a saucer-shaped test vehicle known as a Low Density Supersonic Decelerator is shown in the Missile Assembly Building at the US Navy’s Pacific Missile Range Facility at Kekaha on the island of Kauai in Hawaii.AP/NASA

After several weather delays, NASA on Saturday launched a helium balloon carrying a saucer-shaped vehicle high in Earth’s atmosphere to test technology that could be used to land on Mars.

The craft deployed a novel inflatable braking system on its way back to Earth, but its massive parachute failed to fully unfurl as it descended to a splashdown.

Control room cheers that greeted successful steps in the complex test rapidly died as the parachute appeared to emerge tangled.

“Please inform the recovery director we have bad chute,” a mission official ordered.

Since the twin Viking spacecraft landed on the red planet in 1976, NASA has relied on the same parachute design to slow landers and rovers after piercing through the thin Martian atmosphere.

The $150 million experimental flight tests a novel vehicle and a giant parachute designed to deliver heavier spacecraft and eventually astronauts.

Viewers around the world with an Internet connection followed portions of the mission in real time thanks to cameras on board the vehicle that beamed back low-resolution footage.

After taking off at 11:40 a.m. from the Pacific Missile Range Facility on the Hawaiian island of Kauai, the balloon boosted the disc-shaped vehicle over the Pacific. Its rocket motor should then ignite, carrying the vehicle to 34 miles high at supersonic speeds.

The environment this high up is similar to the thin Martian atmosphere. As the vehicle prepared to drop back the Earth, a tube around it expanded like a Hawaiian puffer fish, creating atmospheric drag to dramatically slow it down from Mach 4, or four times the speed of sound.

Then the parachute if only partially — and the vehicle splashed down about three hours later. At 110 feet in diameter, the parachute is twice as big as the one that carried the 1-ton Curiosity rover through the Martian atmosphere in 2011.

Despite the parachute problem, “what we just saw was a really good test,” said NASA engineer Dan Coatta with the Jet Propulsion Laboratory in Pasadena, California.

The test was postponed six previous times because of high winds. Winds need to be calm so that the balloon doesn’t stray into no-fly zones.

Engineers planned to analyze the data and conduct several more flights next year before deciding whether to fly the vehicle and parachute on a future Mars mission.

“We want to test them here where it’s cheaper before we send it to Mars to make sure that it’s going to work there,” project manager Mark Adler of the NASA Jet Propulsion Laboratory said during a pre-launch news conference in Kauai in early June.

The technology envelope needs to be pushed or else humanity won’t be able to fly beyond the International Space Station in low-Earth orbit, said Michael Gazarik, head of space technology at NASA headquarters.

Technology development “is the surest path to Mars,” Gazarik said at the briefing.

The Los Angeles Times reported that teams working on the project will report at different times. These teams include specialists who will launch the balloon and communication teams. There are antennas near the base, the report said.

There is a lot that can go wrong, but that’s precisely why the teams say these tests are imperative.

“We learn even more when we fail,” Robert Manning, the chief engineer, told The Times. “If you’re not dropping balls, you’re not learning how to juggle.”

Click for more from LA Times

The Associated Press contributed to this report

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Musk: SpaceX could land humans on Mars in 10 to 12 years

Musk: SpaceX could land humans on Mars in 10 to 12 years

SpaceX founder Elon Musk thinks his private spaceflight company will have the capability to land humans on Mars within 12 years, assuming the availability of funding for the historic mission. Also, once SpaceX starts making steps toward this goal, the company could be floated on the stock market to boost investment for the red planet adventure.

Musk, who also founded the electric car manufacturer Tesla, has always made his interplanetary intentions known, but this recent announcement is a reminder about how far the company has come and how far it is looking into the future.

 During the CNBC interview, Musk said: “I’m hopeful that the first people could be taken to Mars in 10 to 12 years, I think it’s certainly possible for that to occur. But the thing that matters long term is to have a self-sustaining city on Mars, to make life multiplanetary.”

Musk also highlighted NASA’s role in SpaceX’s success, pointing out that without the US space agency’s pioneering work that SpaceX wouldn’t be where it is today. NASA provided funding to help develop SpaceX’s Falcon rocket series and Dragon space capsule, eventually awarding the company a $1.6 billion contract to help resupply the International Space Station.

SpaceX is now competing for the next round of NASA contracts that will be awarded to a private US spaceflight company for commercial crew launches to the space station. Musk unveiled the crewed version of the Dragon capsule — dubbed the Dragon “V2″ (version 2) — at the company’s headquarters in Hawthorn, Calif., last month.

The Dragon V2 will be considered in a 3-way competition to acquire NASA contracts to fly astronauts to the space station (and beyond), ending the US dependence on the Russian Soyuz launch vehicle to get astronauts into space after the Space Shuttle fleet was retired in 2011. Aerospace giant Boeing and spaceflight company Sierra Nevada also have potential “space taxis” in the running, but NASA cannot fund them all.

Should SpaceX not win the commercial crew contract, however, Musk is still confident that his ultimate Mars dream can be fulfilled.

“It’s possible that we may not win the commercial crew contract. … We’ll do our best to continue on our own, with our own money,” he said. “We would not be where we are today without the help of NASA.”

SpaceX is hoping to see the maiden flight of the powerful Falcon Heavy rocket within the next year, a booster that could launch heavy components for a Mars mission into space.

A potential route to funding a Mars mission could come if SpaceX went public and floated on the stock market. But with investors comes pressure for the company to be constantly growing and being profitable, momentum that can be difficult to maintain over a multi-year effort toward the one Mars goal.

“We need to get where things a steady and predictable,” Musk said. “Maybe we’re close to developing the Mars vehicle, or ideally we’ve flown it a few times, then I think going public would make more sense.”

While commenting on Tesla’s pioneering work into driving down the cost of electric cars, Musk joked that a mission to Mars may be an easier task than driving down the cost of electric car batteries to less than $5000. He was, however, optimistic that Tesla could start producing a “compelling” mass-market electric car within the next 3 years.

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Details of 1st private manned Mars mission revealed

Details of 1st private manned Mars mission revealed

By Mike Wall

Published November 21, 2013

  • inspiration-mars-spacecraft

    An artist’s illustration of the Inspiration Mars Foundation’s spacecraft for a 2018 mission to Mars by a two-person crew. The private Mars mission would be a flyby trip around the Red Planet. (INSPIRATION MARS FOUNDATION)

  • inspiration-mars-spacecraft-concept

    An artist’s depiction of the planned Inspiration Mars spacecraft to send a married couple on a flyby mission around Mars.(INSPIRATION MARS)

  • inspiration-mars-mission-concept

    This image from an Inspiration Mars fact sheet shows the nonprofit space exploration group’s vision for its planned two-person Mars flyby mission, which it hopes to launch between 2017 and 2018. (INSPIRATION MARS)

  • inspiration-mars-mission-spacecraft-concept

    An artist’s illustration of the manned spacecraft for the Inspiration Mars mission to send two astronauts on a Mars flyby mission in 2017-2018. (INSPIRATION MARS)

A nonprofit space exploration group revealed exactly how it plans to launch two married astronauts on an ambitious manned flyby mission to the Red Planet by early 2018, a scenario that would involve NASA and federal funding along with a healthy dose of the pioneering spirit.

The Inspiration Mars project — which is led by multimillionaire Dennis Tito, the world’s first space tourist — hopes to partner with NASA, using much of the space agency’s equipment and expertise as well as an infusion of federal money to get off the launch pad by early January 2018.

“Perhaps several hundred million dollars in new federal spending can make this mission happen,” Inspiration Mars officials wrote in a report, released Wednesday, that outlines the mission’s proposed architecture. “We now call on our nation’s leaders to seize this singular opportunity to begin human exploration of the solar system and affirm America’s leadership throughout the world.” [Private Mission to Mars Explained (Infographic)]

‘Perhaps several hundred million dollars in new federal spending can make this mission happen.’

– Inspiration Mars officials

The proposed “Mission for America” would launch a married couple toward the Red Planet sometime between Dec. 25, 2017 and Jan. 5, 2018, to take advantage of a rare favorable alignment of Mars and Earth.

The two astronauts would not land on the Red Planet but would cruise within 100 miles of its surface before heading back home, eventually touching down on Earth in May 2019 after spending 501 days in space.

The flyby mission will help inspire the next generation of researchers and engineers, preserving America’s competitive edge in science and technology, Inspiration Mars officials say. It should also lay the foundation for even more ambitious manned exploration of the solar system, they add.

“There’ll be a lot of science return and techology return,” Taber MacCallum, Inspiration Mars’ chief technology officer, told reporters during a teleconference today. “We will, I think, sort of break the sound barrier for going to Mars and back, enabling a range of missions to occur in the future.”

The current mission plan, as outlined in the report, calls for using NASA’s Space Launch System mega-rocket (SLS), which is in development with a first flight slated for late 2017.

The flyby mission would require two launches in quick succession. In the first liftoff, an SLS would loft four payloads to Earth orbit: an SLS upper-stage rocket; a 600-cubic-foot habitat module derived from Orbital Sciences’ Cygnus cargo vessel; a service module that would support the habitat module with power, propulsion and communications systems; and an Earth re-entry pod, which would be based on NASA’s Orion capsule.

The second launch — this one likely using a commercial rocket — would deliver the two astronauts to orbit aboard a yet-to-be-selected private spaceship. The crewmembers would then transfer to the habitat module, and the SLS upper stage would propel them on toward Mars.

The married couple would spend virtually the entire mission in the habitat module, transferring to the re-entry pod in the last few hours of the mission.

Inspiration Mars officials acknowledge that making all of this happen will be challenging. The re-entry pod, for example, will have to protect the astronauts from the blazing heat generated when it slams into Earth’s atmosphere at about 32,000 mph.

But it can be done, and the current plan — which emphasizes the use of technology already proven or in development whenever possible — gives the mission the best chance of success, Inspiration Mars officials say.

“We submit this report with unreserved faith in the men and women of NASA, with a singleminded commitment to surmounting every obstacle, and with complete confidence that this mission can be done,” they write in the report.

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Brightest explosion ever seen in the universe

Brightest explosion ever seen in the universe

By Denise Chow

Published November 22, 2013

  • brightest-gamma-ray-burst

    An unusually bright gamma-ray burst produced a jet that emerged at nearly the speed of light. (NASA/SWIFT/CRUZ DEWILDE)

  • gamma-ray-burst-swift-nasa

    A gamma-ray burst that exploded in April 2013 is the most luminous object in the field, as seen in this image from NASA’s Swift satellite. All the other objects seen in the image are stars from our own galaxy, while the gamma-ray burst is milli (NASA/SWIFT SATELLITE)

  • gamma-ray-burst-swift

    Close-up image of the brightest gamma-ray burst ever seen, taken in April 2013 by the ultraviolet/optical telescope on NASA’s Swift satellite. (NASA/SWIFT SATELLITE)

A mysterious blast of light spotted earlier this year near the constellation Leo was actually the brightest gamma-ray burst ever recorded, and was triggered by an extremely powerful stellar explosion, new research reports.

On April 27, several satellites — including NASA’s Swift satellite and Fermi Gamma-ray Space Telescope — observed an unusually bright burst of gamma radiation. The explosion unleashed an energetic jet of particles that traveled at nearly the speed of light, researchers said.

“We suddenly saw a gamma-ray burst that was extremely bright — a monster gamma-ray burst,” study co-author Daniele Malesani, an astrophysicist at the Niels Bohr Institute at the University of Copenhagen in Denmark, said in a statement. “This [was] one of the most powerful gamma-ray bursts we have ever observed with the Swift satellite.” [Top 10 Strangest Things in Space]

The gamma-ray burst was described in a series of studies published online Thursday in the journal Science.

‘The exploding matter was traveling at [nearly] the speed of light.’

– Giacomo Vianello, a postdoctoral scholar at Stanford University

Gamma-ray bursts, or GRBs, are the most powerful type of explosions in the universe and typically mark the destruction of a massive star. The original stars are too faint to be seen, but the supernova explosions that signal a star’s death throes can cause violent bursts of gamma radiation, researchers said.

Gamma-ray bursts are usually short but extremely bright. Still, ground-based telescopes have a tough time observing them because Earth’s atmosphere absorbs the gamma radiation.

The extremely bright gamma-ray burst seen earlier this year, officially dubbed GRB 130472A, occurred in a galaxy 3.6 billion light-years away from Earth, which, though still far away, is less than half the distance at which gamma-ray bursts have previously been seen. This closer proximity to Earth enabled astronomers to confirm for the first time that one object can simultaneously create a powerful GRB and a supernova explosion.

“We normally detect GRBs at great distance, meaning they usually appear quite faint,” study co-author Paul O’Brien, an astronomer at the University of Leicester in the United Kingdom, said in a statement. “In this case, the burst happened only a quarter of the way across the universe — meaning it was very bright. On this occasion, a powerful supernova was also produced — something we have not recorded before alongside a powerful GRB — and we will now be seeking to understand this occurrence.”

The jet produced by the gamma-ray burst was formed when a massive star collapsed on itself and created a black hole at its center. This generated a blast wave that caused the stellar remnants to expand, producing a glowing shell of debris that was observed as an extremely bright supernova explosion.

After analyzing properties of the light produced by the gamma-ray burst, scientists determined that the original star was only three to four times the size of the sun, but was 20 to 30 times more massive. This extremely compact star was also rapidly rotating, the researchers said.

The GRB was the brightest and most energetic ever witnessed and triggered dynamic internal and external shock waves that are still not well understood. Though scientists have a clearer view of the violent explosion, mysteries remain. For instance, space telescopes detected more photons and more high-energy gamma-rays than theoretical models predicted for a gamma-ray burst of this magnitude.

Researchers are still investigating why the energy levels seen with GRB 130472A do not quite match predictions from existing models of gamma-ray bursts. Their results could lead to more refined theories about how particles are accelerated, which could help astronomers better predict the behavior of cosmic events.

“The really cool thing about this GRB is that because the exploding matter was traveling at [nearly] the speed of light, we were able to observe relativistic shocks,” study co-author Giacomo Vianello, a postdoctoral scholar at Stanford University in California, said in a statement. “We cannot make a relativistic shock in the lab, so we really don’t know what happens in it, and this is one of the main unknown assumptions in the model. These observations challenge the models and can lead us to a better understanding of physics.”

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Lunar Craters Covering Moon’s Near Side Are Bigger Than Far Side

Lunar Craters Covering Moon’s Near Side Are Bigger Than Far Side Due To Hemisphere Differences

natureheader  |  By Davide CastelvecchiPosted: 11/08/2013 9:07 am EST  |  Updated: 11/08/2013 9:43 am EST

 
lunar craters

When the Soviet probe Luna 3 sent back the first shots of the dark side of the Moon, they showed that it was noticeably more pockmarked by craters than the near side. The nearside crust, by contrast, had more large, shallow basins. More than 50 years after those images first baffled researchers,a study published today in Science explains the observations.

Some theories suggest that the large basins on the near side were caused by impacts from asteroids bigger than those that caused the craters on the far side. But the latest study suggests that the observed basins do not accurately reflect the size of the initial impact, because as asteroids battered the lunar surface in the early history of the Solar System, the Moon’s warmer and softer nearside crust melted like butter, producing giant lava flows that filled the impact craters and transformed them into basins.

To improve on previous estimates of the size and distribution of basins, the team behind the study used data from NASA’s Gravity Recovery and Interior Laboratory mission (GRAIL), two satellites that since 2011 have been orbiting the Moon and mapping subtle variations in the strength of its gravitational field. Basins are characterized by thinner crust, says first author Katarina Miljković, a planetary scientist at the Paris Institute of Earth Physics. The team used GRAIL’s gravity mapsto find such thin crust and measure the true size of the basins.

“We didn’t have to look at topography nearly at all, just at the crust thickness,” says Miljković. The researchers found that although both sides of the Moon had the same total number of impact craters, the near side had eight basins larger than 320 kilometers in diameter, whereas the far side had only one.

 Hot hit

 The asteroid bombardment should have battered both sides equally, Miljković points out. The asymmetry could have arisen from comparatively small objects punching above their weight on the near side, producing basins more easily than on the far side.

Simulations showed that if the largest dark area on the near side — the plain of volcanic rock known as Oceanus Procellarum — was hundreds of degrees hotter than crust on the far side, impacts there would produce basins up to twice as large as impacts from similar-sized bodies on the far side (see video above).

And indeed, around 4 billion years ago, or 500 million years after the Moon formed, the near side could have been warmer than the far side. Researchers looking at the near side have detected the presence of radioactive isotopes; their decay would have heated up the rock, explains study co-author Maria Zuber, a planetary scientist at the Massachusetts Institute of Technology in Cambridge and principal investigator of GRAIL.

The findings fit well with the observations, but “there is no consensus” as to what caused the startling asymmetry in isotope content between the near side and the far side, says Jeffrey Taylor, a lunar scientist at the University of Hawaii in Honolulu. One leading theory posits that material rich in radioactive elements rose in a gigantic volcanic plume and formed a magma basin; another that it came from a collision with a sister moon around 1,000 kilometers in diameter.

William Bottke, a lunar scientist at the Southwest Research Institute in Boulder, Colorado, says that the work could lead researchers to revise just how dramatic asteroid bombardments were in the early Solar System. “This can be used to more accurately derive what the small-body populations were like four billion years ago.”

This story originally appeared in Nature News.

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