Archives of astronomy blog

January 15, 2009, 6:30 PM CT

Mars is not a dead planet

This image shows concentrations of Methane discovered on Mars.

Credit: NASA

A team of NASA and university researchers has achieved the first definitive detection of methane in the atmosphere of Mars. This discovery indicates the planet is either biologically or geologically active.

The team found methane in the Martian atmosphere by carefully observing the planet throughout several Mars years with NASA's Infrared Telescope Facility and the W.M. Keck telescope, both at Mauna Kea, Hawaii. The team used spectrometers on the telescopes to spread the light into its component colors, as a prism separates white light into a rainbow. The team detected three spectral features called absorption lines that together are a definitive signature of methane.

"Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas," said Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md. "At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif." Mumma is main author of a paper describing this research that will appear in Science Express on Thursday.

Methane, four atoms of hydrogen bound to a carbon atom, is the main component of natural gas on Earth. Astrobiologists are interested in these data because organisms release much of Earth's methane as they digest nutrients. However, other purely geological processes, like oxidation of iron, also release methane.........

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January 8, 2009, 9:55 PM CT

Looking through Galileo's eyes

In 1609, exactly four centuries ago, Galileo revolutionised humankind's understanding of our position in the Universe when he used a telescope for the first time to study the heavens, which saw him sketching radical new views of the moon and discovering the satellites orbiting Jupiter.

In synch with the International Year of Astronomy (IYA), which marks the 400th anniversary of Galileo's discoveries, a group of astronomers and curators from the Arcetri Observatory and the Institute and Museum of the History of Science, both in Florence, Italy, are recreating the kind of telescope and conditions that led to Galileo's world-changing observations, reports January's Physics World

Astronomers will be using the recreated apparatus to catalogue all the objects recorded in Galileo's 'Sidereus Nuncius' (or, in English, "Starry Messenger"), the treatise that Galileo published in 1610 which included a number of of his early observations.

The team has already observed the Moon and Saturn and are now recording images of Jupiter's moons and the phases of Venus, both of which provided crucial evidence to confirm the heliocentric hypothesis and prove that the Earth is not the centre of the Universe.

To recreate the apparatus, the team undertook a painstaking investigation of the nature of the lens of a telescope given to Galileo's patron, the Grand Duke of Tuscany, Cosimo II, in 1610. That work involved measuring the shape and refractive index of the lens, and using X-ray fluorescence to determine the condition of the glass. The group now plans to put the images seen by the telescope online. Sadly, the team has not been able to build a replica of the telescope actually used by Galileo to make the observations reported in Sidereus Nuncius as only one lens of that instrument survives.........

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January 8, 2009, 9:11 PM CT

How Martian winds make rocks walk

These Spirit Rover camera images of the intercrater plain between Mars' Lahontan Crater show uniformly-spaced small rocks, known as clasts. The image on the left is a portion of NAVCAM image ID 2 N 137561115 EFF 47 00 P1827 L0 M1. The image on the right is a portion of Pancam image 2 P 137636467 EFF 47 DQ P2514 R1 C1.

Credit: Geological Society of America.

Rocks on Mars are on the move, rolling into the wind and forming organized patterns, as per new research.

The new finding counters the prior explanation of the evenly spaced arrangement of small rocks on Mars. That explanation suggested the rocks were picked up and carried downwind by extreme high-speed winds thought to occur on Mars in the past.

Images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about 5 to 7 centimeters apart on the intercrater plains between Lahontan Crater and the Columbia Hills.

Eventhough Mars is a windy planet, it would be difficult for the wind to carry the small rocks, which range in size from a quarter to a softball, said Jon D. Pelletier, associate professor of geosciences at The University of Arizona in Tucson.

Pelletier and colleagues suggest that wind blows sand away from the front of the rock, creating a pit, and then deposits that sand behind the rock, creating a hill.

The rock then rolls forward into the pit, moving into the wind, he said.

As long as the wind continues to blow, the process is repeated and the rocks move forward.

This explanation does not require extreme winds, Pelletier said.

"You get this happening five, 10, 20 times then you start to really move these things around," he said. "They can move a number of times their diameter".........

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January 7, 2009, 11:50 PM CT

Asteroids with Earth-like Crust

Field image of the achondrite meteorite GRA 06128, found in blue ice of the Graves Nunatak region of the Antarctica during the ANSMET 2006/2007 field-season.

Image courtesy of the Antarctic Search for Meteorites (ANSMET 2006-2007 PI - Ralph Harvey, Case Western Reserve University).

Two rare meteorites found in Antarctica two years ago are from a previously unknown, ancient asteroid with an outer layer or crust similar in composition to the crust of Earth's continents, reports a research team primarily composed of geochemists from the University of Maryland.

Reported in the January 8 issue of the journal Nature, this is the first ever finding of material from an asteroid with a crust like Earth's. The discovery also represents the oldest example of rock with this composition ever found.

These meteorites point "to previously unrecognized diversity" of materials formed early in the history of the Solar System, write authors James Day, Richard Ash, Jeremy Bellucci, William McDonough and Richard Walker of the University of Maryland; Yang Liu and Lawrence Taylor of the University of Tennessee and Douglas Rumble III of the Carnegie Institution for Science.

Prof. James Day looking at a portion of the meteorite in the University of Maryland's isotope geochemistry lab. In the background is a mass spectrometer used to analyze the meteorite samples.

"What is most unusual about these rocks is that they have compositions similar to Earth's andesite continental crust -- what the rock beneath our feet is made of," said first author Day, who is a research scientist in Maryland's department of geology. "No meteorites like this have ever been seen before".........

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January 6, 2009, 9:09 PM CT

Black Holes Lead Galaxy Growth

VLA image (right) of gas in young galaxy seen as it was
when the Universe was only 870 million years old.
CREDIT: NRAO/AUI/NSF, SDSS

Astronomers may have solved a cosmic chicken-and-egg problem -- the question of which formed first in the early Universe -- galaxies or the supermassive black holes seen at their cores.

"It looks like the black holes came first. The evidence is piling up," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO). Carilli outlined the conclusions from recent research done by an international team studying conditions in the first billion years of the Universe's history in a lecture presented to the American Astronomical Society's meeting in Long Beach, California.

Earlier studies of galaxies and their central black holes in the nearby Universe revealed an intriguing linkage between the masses of the black holes and of the central "bulges" of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to a number of billions of times the mass of our Sun, the black hole's mass is about one one-thousandth of the mass of the surrounding galactic bulge.

"This constant ratio indicates that the black hole and the bulge affect each others' growth in some sort of interactive relationship," said Dominik Riechers, of Caltech. "The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process".........

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January 6, 2009, 8:49 PM CT

From The Static To The Dynamic

Two new efforts have taken a famous supernova remnant from the static to the dynamic. A new movie of data from NASA's Chandra X-ray Observatory shows changes in time never seen before in this type of object. A separate team will also release a dramatic three-dimensional visualization of the same remnant.

Nearly ten years ago, Chandra's "First Light" image of Cassiopeia A (Cas A) revealed previously unseen structures and detail. Now, after eight years of observation, researchers have been able to construct a movie that tracks the remnant's expansion and changes over time.

"With Chandra, we have watched Cas A over a relatively small amount of its life, but so far the show has been amazing," said Daniel Patnaude of the Smithsonian Astrophysical Observatory in Cambridge, Mass. "And, we can use this to learn more about the aftermath of the star's explosion".

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December 16, 2008, 10:17 PM CT

Caltech researchers interpret asymmetry in early universe

This is the cosmic microwave background as seen by the WMAP satellite. This radiation was emitted when the Universe was 380,000 years old and has an average temperature of 2.7 Kelvin. The red and blue spots are temperature fluctuations that differ from the average temperature by only 0.0002 degrees. The region of maximal variation is in the lower right quadrant.

Credit: NASA/WMAP Science Team

The Big Bang is widely considered to have obliterated any trace of what came before. Now, astrophysicists at the California Institute of Technology (Caltech) believe that their new theoretical interpretation of an imprint from the earliest stages of the universe may also shed light on what came before.

"It's no longer completely crazy to ask what happened before the Big Bang," comments Marc Kamionkowski, Caltech's Robinson Professor of Theoretical Physics and Astrophysics. Kamionkowski joined graduate student Adrienne Erickcek and senior research associate in physics Sean Carroll to propose a mathematical model explaining an anomaly in what is supposed to be a universe of uniformly distributed radiation and matter.

Their investigations turn on a phenomenon called inflation, first proposed in 1980, which posits that space expanded exponentially in the instant following the Big Bang. "Inflation starts the universe with a blank slate," Erickcek describes. The hiccup in inflation, however, is that the universe is not as uniform as the simplest form of the theory predicts it to be. Some parts of it are more intensely varied than others.

Until recently, measurements of the Cosmic Microwave Background (CMB) radiation, a form of electromagnetic radiation that permeated the universe 400,000 years after the Big Bang, were consistent with inflation--miniscule fluctuations in the CMB seemed to be the same everywhere. But a few years ago, some researchers, including a group led by Krzysztof Gorski of NASA's Jet Propulsion Laboratory, which is managed by Caltech, scrutinized data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP). They discovered that the amplitude of fluctuations in the CMB is not the same in all directions.........

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December 16, 2008, 9:39 PM CT

Biggest breach of Earth's solar storm shield discovered

NASA's THEMIS mission has overturned a longstanding belief about the interaction between solar particles and Earth's magnetic field.

Credit: NASA

Earth's magnetic field, which shields our planet from particles streaming outward from the Sun, often develops two holes that allow the largest leaks, as per scientists sponsored by NASA and the National Science Foundation.

"The discovery overturns a long-standing belief about how and when most of the solar particles penetrate Earth's magnetic field, and could be used to predict when solar storms will be severe. Based on these results, we expect more severe storms during the upcoming solar cycle," said Vassilis Angelopoulos of the University of California, Los Angeles, Principal Investigator for NASA's THEMIS mission (Time History of Events and Macroscale Interactions during Substorms). THEMIS was used to discover the size of the leak.

Earth's magnetic field acts as a shield against the bombardment of particles continuously streaming from the sun. Because the solar particles (ions and electrons) are electrically charged, they feel magnetic forces and most are deflected by our planet's magnetic field. However, our magnetic field is a leaky shield and the number of particles breaching this shield depends on the orientation of the sun's magnetic field. It had been thought that when the sun's magnetic field is aligned with that of the Earth, the door is shut and that few if any solar particles enter Earth's magnetic shield. The door was thought to open up when the solar magnetic field direction points opposite to Earth's field, leading to more solar particles inside the shield.........

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December 15, 2008, 9:34 PM CT

Explanation for Migration of Volcanic Activity on Mars

Picture a ball. It's an ordinary ball in every way except that it is roughly 4,300 miles in diameter and is moving through the cold of space some 35 million miles from Earth, and hurtling around the sun in just less than two Earth years. This is Mars.

After a first glance at the Martian surface, one may quickly notice two striking global-scale features. The first is the three-mile elevation difference between the northern lowlands and southern highlands, known as the Crustal Dichotomy, which got the name because the highlands and lowlands are underlain by thick and thin crust, respectively. The second feature is the vast area of high elevation with numerous volcanoes near the equator covering a quarter of the Martian surface, known as the Tharsis Rise.

For a moment consider the tectonic plates that make up the crust of the Earth, including the way they move around the planet, rising from below as molten rock and dipping back down under the surface to melt and complete the chain. Earth is the only planet known to researchers that has this mechanism for moving huge sections of the planet's surface great distances. This movement accounts for, among other things, the chain of land masses that form the Hawaiian Islands. As the Pacific Plate moves over a plume of molten rock, the islands formed, one after another.........

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December 15, 2008, 9:32 PM CT

Solar Flare Surprise

The X9-class solar flare of Dec. 5, 2006, observed by the Solar X-Ray Imager aboard NOAA's GOES-13 satellite. Credit: NOAA's Space Weather Prediction Center

Solar flares are the most powerful explosions in the solar system. Packing a punch equal to a hundred million hydrogen bombs, they obliterate everything in their immediate vicinity. Not a single atom should remain intact.

At least that's how it's supposed to work.

"We've detected a stream of perfectly intact hydrogen atoms shooting out of an X-class solar flare," says Richard Mewaldt of the California Institute of Technology. "What a surprise! If we can understand how these atoms were produced, we'll be that much closer to understanding solar flares".

The event occurred on Dec. 5, 2006. A large sunspot rounded the sun's eastern limb and with little warning it exploded. On the "Richter scale" of flares, which ranks X1 as a big event, the blast registered X9, making it one of the strongest flares of the past 30 years.

NASA managers braced themselves. Such a ferocious blast commonly produces a blizzard of high-energy particles dangerous to both satellites and astronauts. An hour later they arrived, but they were not the particles scientists expected.

NASA's twin Solar TErrestrial RElations Observatory (STEREO) spacecraft made the discovery: "It was a burst of hydrogen atoms," says Mewaldt. "No other elements were present, not even helium (the sun's second-most abundant atomic species). Pure hydrogen streamed past the spacecraft for a full 90 minutes".........

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