NASA's Near-Earth Object Office says that new observations of comet C/2013 A1 (Siding Spring) have allowed further refinements of the comet's orbit, helping to determine the chances it could hit Mars in October of 2014. Shortly after its discovery in December 2012, astronomers thought there was an outside chance that a newly discovered comet might be on a collision course with Mars.

While the latest orbital plot places the comet's closest approach to Mars slightly closer than previous estimates, the new data now significantly reduces the probability the comet will impact the Red Planet, JPL said, from about 1 in 8,000 to about 1 in 120,000.

The closest approach is now estimated at about 68,000 miles (110,000 kilometers). The most previous estimates had it whizzing by at 186,000 miles (300,000 kilometers).

A group of Russian space enthusiasts may have found the location of the first space probe ever to land on Mars, the 42-year-old Mars-3.

In a post Thursday, NASA highlighted pictures taken from the Mars Reconnaissance Orbiter near the location of the Curiosity rover.

"In 1971, the former Soviet Union launched the Mars 2 and Mars 3 missions to Mars. Each consisted of an orbiter plus a lander," NASA said. "Both orbiter missions succeeded, although the surface of Mars was obscured by a planet-encircling dust storm. The Mars 2 lander crashed. Mars 3 became the first successful soft landing on the Red Planet, but stopped transmitting after just 14.5 seconds for unknown reasons."

The Russian group, which comes together online as a Mars Curiosity Rover community, started searching through images from the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. Through crowdsourcing, it wasn't long until they found something.

Carbon-dating of an ancient beam from a Guatemalan temple may help end a century-long debate about the Mayan calendar, anthropologists said on Thursday.

Experts have long wrangled over how the Mayan calendar - which leapt to global prominence last year when the superstitious said it predicted the end of the world - correlates to the European calendar.

Texts and carvings from this now-extinct culture describe rulers and great events and attribute the dates according to a complex system denoted by dots and bars, known as the Long Count.

The Long Count consists of five time units: Bak'tun (144,000 days); K'atun (7,200 days), Tun (360 days), Winal (20 days) and K'in (one day).

The time is counted from a mythical starting point.

But the date of this starting point is unknown. Spanish colonisers did their utmost to wipe out traces of the Mayan civilisation, destroying evidence that could have provided a clue.

An example of the confusion this has caused is the date of a decisive battle that shaped the course of Mayan civilisation.

Cbet nr. 3472, issued on 2013, April 04, announces the discovery of a new comet (discovery magnitude ~20.7) by PANSTARRS survey on CCD images obtained with the 1.8-m Pan-STARRS1 telescope on Haleakala on April 10.4. The new comet has been designated C/2013 G3 (PANSTARRS).

We performed follow-up measurements of this object, while it was still on the neocp. Stacking of 11 R-filtered exposures, 50-sec each, obtained remotely on 2013, April 11.4 from E10 Faulkes Telescope South through a 2.0-m f/10.0 Ritchey-Chretien + CCD, shows that this object is slightly diffused.The FWHM of this object was measured about 20% wider than that of nearby field stars of similar brightness. Below you can see our image.

Committee overwhelmingly votes down privacy amendments that would have curbed National Security Agency's access to private sector data. Now the bill heads to the House floor for a vote.

A controversial data-sharing bill won the approval of a key congressional committee today without privacy amendments, raising concerns that the National Security Agency and other spy agencies will gain broad access to Americans' personal information.

The House Intelligence committee, by a vote of 18 to 2, adopted the so-called CISPA bill after an unusual session closed to the public where panel members debated and voted on the proposed law in secret.

Rep. Jan Schakowsky (D-Ill.), who proposed three unsuccessful privacy amendments, said afterward she was disappointed her colleagues did not limit the NSA and other intelligence agencies from collecting sensitive data on Americans. (See CNET's CISPA FAQ.)

Her privacy amendments would have "required that companies report cyber threat information directly to civilian agencies, and maintained the long-standing tradition that the military doesn't operate on U.S. soil against American citizens," Schakowsky said.

Discovery Date: April 8, 2013

Magnitude: 17.0 mag

Discoverer: Robert H. McNaught (Siding Spring)

The orbital elements are published on M.P.E.C. 2013-G39.

Denver - The size of a proton, long thought to be well-understood, may remain a mystery for a while longer, according to physicists.

Speaking today (April 13) at the April meeting of the American Physical Society, researchers said they need more data to understand why new measurements of proton size don't match old ones.

"The discrepancy is rather severe," said Randolf Pohl, a scientist at the Max Planck Institute of Quantum Optics. The question, Pohl and his colleagues said, is whether the explanation is a boring one - someone messed up the measurements - or something that will generate new physics theories.

The incredible shrinking proton

The proton is a positively charged particle in the nucleus of atoms, the building blocks of everything. Years of measurements pegged the proton at 0.8768 femtometers in radius (a femtometer is a millionth of a billionth of a meter).

But a new method used in 2009 found a different measurement: 0.84087 femtometers, a 4 percent difference in radius.

The previous measurements had used electrons, negatively charged particles that circle the nucleus in a cloud, to determine proton radius. To make the measurement with electrons, researchers can do one of two things. First, they can fire electrons at protons to measure how the electrons are deflected. This electron-scattering method provides insight into the size of the positively charged proton.

An alternative is to try to make the electron move. Electrons zing around the nucleus of an atom, where protons reside, at different levels called orbitals. They can jump from orbital to orbital by increasing or decreasing their energy, which electrons do by losing or gaining an elementary particle of light called a photon. The amount of energy it takes to budge an electron from orbital to orbital tells physicists how much pull the proton has, and thus the proton's size.

Pohl and his colleagues didn't use electrons at all in their measurements of the proton. Instead, they turned to another negatively charged particle called the muon. The muon is 200 times heavier than an electron, so it orbits the proton 200 times closer. This heft makes it easier for scientists to predict which orbital a muon resides in and thus a much more sensitive measure of proton size.

"The muon is closer to the proton and it has a better view," Pohl said.

Many saw it coming, but that didn't stop the Bitcoin bubble from bursting: after rising to dizzying heights, the digital currency suffered its first true crash this week.

The price of the virtual "geek" currency had soared through the stratosphere in recent weeks, trading for a high of $266 on Wednesday - only to come hurtling back to Earth in just three days.

By Friday, a single Bitcoin was worth just $54, according to the Mt. Gox platform, which manages 80 percent of the Bitcoin transactions and had to briefly shut down trading Thursday.

"There was a LOT of short-term speculation happening" from people who wanted to earn a buck from the soaring prices and cash out before the fall, Bitcoin Foundation chief scientist Gavin Andresen told AFP.

"Wild price swings are not good for Bitcoin."

Star Wars defense planned for Persian Gulf debut in 2014

The US Navy says it has successfully test-fired a ship-mounted laser weapon, and that it plans to deploy the device to an actual maritime staging area beginning in 2014.

On Monday, the Navy released video and still images showing the somewhat-unimaginatively named Laser Weapon System (LaWS) firing on an unmanned drone, causing the aircraft to burst into flames and plummet from the sky.

Speaking at the Navy League Sea Air Space Exposition at National Harbor, Maryland on Monday, Rear Admiral Matthew Klunder, chief of Naval research, said the device would be deployed to the Persian Gulf, where Iran has been "harassing" US ships with drones and small, fast boats.

"The area we're going to test this in is a very intensive maritime region of the world," Klunder told USNI News. "Lots of commerce, lots of ships."

Klunder said the Navy has field-tested the solid-state laser 12 times so far, and in each case it managed to destroy its target. He added that the weapon also has a nonlethal mode that can generate a "dazzle" effect, which can be used to blind enemy vessels by overwhelming their sensors.

In addition to being effective against small, fast-moving craft, the cannon offers another benefit: its low cost relative to traditional weapons systems. According to The New York Times, firing LaWS costs less than $1 per sustained pulse. Compare that to the cost of a short-range interceptor missile, which the paper estimates run around $1.4m apiece.