Monday, April 28, 2014

X-class Flare Erupts from Sun on April 24

NASA's Solar Dynamics Observatory sees an X-class flare exploding off the right side of the sun. This image shows light in the 131-angstrom wavelength, which is particularly good for seeing material at the high temperatures present in solar flares and which is typically colorized in teal.
The sun emitted a significant solar flare, peaking at 8:27 p.m. EDT on April 24, 2014. Images of the flare were captured by NASA's Solar Dynamics Observatory. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel.

This flare is classified as an X1.4 flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.

NASA's Solar Dynamics Observatory sees an X-class flare exploding off the right side of the sun. These three views of the X1.4 flare are in 131, 304 and 171 angstrom.
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Sunday, April 27, 2014

Curiosity Rover Report (Feb. 14, 2014)

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NASA Mars Orbiter Spies Rover Near Martian Butte

NASA's Curiosity Mars rover and tracks from its driving are visible in this view from orbit, acquired on April 11, 2014, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
Image Credit:   NASA/JPL-Caltech/Univ. of Arizon

Scientists using NASA's Curiosity Mars rover are eyeing a rock layer surrounding the base of a small butte, called "Mount Remarkable," as a target for investigating with tools on the rover's robotic arm.

The rover works near this butte in an image taken on April 11 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter
A rover's-eye view of Mount Remarkable and surroundings as seen from Curiosity's position in that HiRISE image is available in a mosaic of images from Curiosity's Navigation Camera (Navcam).

The butte stands about 16 feet (5 meters) high. Curiosity's science team refers to the rock layer surrounding the base of Mount Remarkable as the "middle unit" because its location is intermediate between rocks that form buttes in the area and lower-lying rocks that show a pattern of striations.

Depending on what the mission scientists learn from a close-up look at the rock and identification of chemical elements in it, a site on this middle unit may become the third rock that Curiosity samples with its drill. The rover carries laboratory instruments to analyze rock powder collected by the drill. The mission's first two drilled samples, in an area called Yellowknife Bay near Curiosity's landing site, yielded evidence last year for an ancient lakebed environment with available energy and ingredients favorable for microbial life.

The rover's current location, where multiple types of rocks are exposed close together, is called "the Kimberley." Here and, later, at outcrops on the slope of Mount Sharp inside Gale Crater, researchers plan to use Curiosity's science instruments to learn more about habitable past conditions and environmental changes
NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington. The project designed and built Curiosity and operates the rover on Mars.

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Monday, April 21, 2014

Alien Atmospheres


NASA Space Assets Detect Ocean inside Saturn Moon


      NASA's Cassini spacecraft and Deep Space Network have uncovered evidence Saturn's moon Enceladus harbors a large underground ocean of liquid water, furthering scientific interest in the moon as a potential home to extraterrestrial microbes.

Researchers theorized the presence of an interior reservoir of water in 2005 when Cassini discovered water vapor and ice spewing from vents near the moon's south pole. The new data provide the first geophysical measurements of the internal structure of Enceladus, consistent with the existence of a hidden ocean inside the moon. Findings from the gravity measurements are in the Friday April 4 edition of the journal Science.
"The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle used with a speed-measuring radar gun," said Sami Asmar of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., a coauthor of the paper. "As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we're trying to measure. We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system."

The gravity measurements suggest a large, possibly regional, ocean about 6 miles (10 kilometers) deep, beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick. The subsurface ocean evidence supports the inclusion of Enceladus among the most likely places in our solar system to host microbial life. Before Cassini reached Saturn in July 2004, no version of that short list included this icy moon, barely 300 miles (500 kilometers) in diameter.

"This then provides one possible story to explain why water is gushing out of these fractures we see at the south pole," said David Stevenson of the California Institute of Technology, Pasadena, one of the paper's co-authors.

Cassini has flown near Enceladus 19 times. Three flybys, from 2010 to 2012, yielded precise trajectory measurements. The gravitational tug of a planetary body, such as Enceladus, alters a spacecraft's flight path. Variations in the gravity field, such as those caused by mountains on the surface or differences in underground composition, can be detected as changes in the spacecraft's velocity, measured from Earth.
The technique of analyzing a radio signal between Cassini and the Deep Space Network can detect changes in velocity as small as less than one foot per hour (90 microns per second). With this precision, the flyby data yielded evidence of a zone inside the southern end of the moon with higher density than other portions of the interior

The south pole area has a surface depression that causes a dip in the local tug of gravity. However, the magnitude of the dip is less than expected given the size of the depression, leading researchers to conclude the depression's effect is partially offset by a high-density feature in the region, beneath the surface.

"The Cassini gravity measurements show a negative gravity anomaly at the south pole that however is not as large as expected from the deep depression detected by the onboard camera," said the paper's lead author, Luciano Iess of Sapienza University of Rome. "Hence the conclusion that there must be a denser material at depth that compensates the missing mass: very likely liquid water, which is seven percent denser than ice. The magnitude of the anomaly gave us the size of the water reservoir."

There is no certainty the subsurface ocean supplies the water plume spraying out of surface fractures near the south pole of Enceladus, however, scientists reason it is a real possibility. The fractures may lead down to a part of the moon that is tidally heated by the moon's repeated flexing, as it follows an eccentric orbit around Saturn.

Much of the excitement about the Cassini mission's discovery of the Enceladus water plume stems from the possibility that it originates from a wet environment that could be a favorable environment for microbial life.
"Material from Enceladus’ south polar jets contains salty water and organic molecules, the basic chemical ingredients for life," said Linda Spilker, Cassini's project scientist at JPL. "Their discovery expanded our view of the 'habitable zone' within our solar system and in planetary systems of other stars. This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington. 

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Sunday, April 20, 2014

NASA Hubble Team Finds Monster "El Gordo" Galaxy Cluster Bigger Than Thought

 NASA's Hubble Space Telescope has weighed the largest known galaxy cluster in the distant universe, catalogued as ACT-CL J0102-4915, and found it definitely lives up to its nickname -- El Gordo (Spanish for "the fat one").

By measuring how much the cluster's gravity warps images of galaxies in the distant background, a team of astronomers has calculated the cluster's mass to be as much as 3 million billion times the mass of our sun. Hubble data show the galaxy cluster, which is 9.7 billion light-years away from Earth, is roughly 43 percent more massive than earlier estimates.

The team used Hubble to measure how strongly the mass of the cluster warped space. Hubble's high resolution allowed measurements of so-called "weak lensing," where the cluster's immense gravity subtly distorts space like a funhouse mirror and warps images of background galaxies. The greater the warping, the more mass is locked up in the cluster.

"What I did is basically look at the shapes of the background galaxies that are farther away than the cluster itself," explained lead author James Jee of the University of California at Davis. "It's given us an even stronger probability that this is really an amazing system very early in the universe."

A fraction of this mass is locked up in several hundred galaxies that inhabit the cluster and a larger fraction is in hot gas that fills the entire volume of the cluster. The rest is tied up in dark matter, an invisible form of matter that makes up the bulk of the mass of the universe.

Though equally massive galaxy clusters are found in the nearby part of the universe, such as the Bullet cluster, nothing like this has ever been discovered to exist so far back in time, when the universe was roughly half its current estimated age of 13.8 billion years. The team suspects such monster galaxy clusters are rare in the early universe, based on current cosmological models.

The immense size of El Gordo was first reported in January 2012. Astronomers estimated its mass based on observations made by NASA's Chandra X-ray Observatory, and galaxy velocities measured by the European Southern Observatory's Very Large Telescope array in Paranal, Chile. They were able to put together estimates of the cluster's mass based on the motions of the galaxies moving inside the cluster and the temperatures of the hot gas between those galaxies.

The challenge was that El Gordo looked as if it might have been the result of a titanic collision between a pair of galaxy clusters -- an event researchers describe as two cosmic cannonballs hitting each other.

"We wondered what happens when you catch a cluster in the midst of a major merger and how the merger process influences both the X-ray gas and the motion of the galaxies," explained John Hughes of Rutgers University. "So, the bottom line is because of the complicated merger state, it left some questions about the reliability of the mass estimates we were making."

That is where the Hubble data came in, according to Felipe Menanteau of the University of Illinois at Urbana-Champaign.

"We were in dire need for an independent and more robust mass estimate given how extreme this cluster is and how rare its existence is in the current cosmological model. There was all this kinematic energy that was unaccounted for and could potentially suggest that we were actually underestimating the mass," Menanteau said. 

The expectation of "unaccounted energy" comes from the fact the merger of galaxy clusters is occurring tangentially to the observers' line-of-sight. This means they are potentially missing a good fraction of the kinetic energy of the merger because their spectroscopic measurements only track the radial speeds of the galaxies.

The team's next step with Hubble will be to compile an image of the cluster. Because El Gordo does not fit into Hubble's field of view, the team will capture images of sections of the galaxy cluster and piece them together into a mosaic.

Researchers say it is like observing a giant from the side.

"We can tell it's a pretty big El Gordo, but we don't know what kind of legs he has, so we need to have a larger field of view to get the complete picture of the giant," said Menanteau
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

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