Archive for the ‘Other Contributors’ Category

Methane on Mars: Extremophiles or Geothermal ?

Monday, February 9th, 2009 by Evan Finnes

Could the detection of methane on Mars be an indication of microbial life, or is a geologic process causing this chemical anomaly?    Prior to 2003, no methane was observed in the Martian atmosphere, beginning on 2003 methane was detected using three ground-based infrared spectrometers.  This Methane was then observed over a three year period (seven Earth years).  The largest plumes were observed during the summer months, the largest contained approximately 19000 metric tons of methane.

The Martian atmosphere is composed of 95% carbon dioxide, 2.7% nitrogen, .07% carbon monoxide, .13% oxygen, 1.6% argon, and trace amounts of water vapor.   Small amounts of methane may be produced due to atmospheric processes but would be relatively short lived due to the ionization of the compound, caused by UV radiation.  Therefore any large amounts of methane present in the atmosphere would have to be the result of the release of a subsurface reservoir.  The origin of such methane reservoirs is unknown, but could be due to biologic or natural processes. 

If 90% of Earth’s methane is produced by life forms, could the methane on Mars also be produced biologically?  Extremophiles could live deep below the surface of Mars where they could use hydrogen as an energy source; this energy could be produced when water exposed to radiation is dissociated into H2 and oxygen.  This reaction also reduces carbon dioxide to methane, which could accumulate in subsurface reservoir s.  If these reservoirs are connected to the surface along faults or fractures, seasonal variations could result in the opening of such cracks which could lead to the release of any methane accumulations.  Extremophiles of this type can be found 3 km below the Witwatersrand Basin of South Africa. 

Another possible source of the methane deposits could be of geologic origin.  Such processes could include the production of magma, or the serpentinization of basalt.  Either of these possibilities could also result in the buildup of subsurface methane deposits.  Much like the extremophile scenario, these deposits could also be released due to the temperature variations that occur with seasonal changes.

The methane appears in highest concentrations at three regions:  Arabia Terra, Nili Fossae, and the South-East corner of Syrtis Major.  The Mars Reconnaissance Orbiter and Mars Express observed that the outcrops in the Nili Fossae region are rich in hydrated minerals.  This suggests that this area resides above a magma chamber.  The largest plume was observed over shield volcano located between Sytris Major and Nili Fossae.  This further suggests that the area is above a magma chamber, and that the production of magma, or the serpentinization of basalt is responsible for the release of the methane plumes, and are probably not the result of the presents of Martian extremophiles.        

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Proposed Space Weapon Ban

Friday, February 6th, 2009 by William Reynolds

It will be interesting to see whether informal rules can be enforced on a global scale to govern space conduct, and whether these will fall along the lines of universality as witnessed with maritime rules of engagement.  This does appear to be the next ominous specter on the not so distant horizon.  What was that song the Beatles sang in 67….All You Need Is Love?  Can anyone today listen to this song with a straight face?  Sigh….

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Stellar Cannibalism Makes Massive Stars

Thursday, January 29th, 2009 by Bellatrix

Another mystery about stellar evolution may have an answer. A group of astronomers looking at globular clusters think they have figured out the origin of a particular type of star known as a blue straggler. The evidence is not concrete but definitely seems to present a plausible answer to a plaguing mystery.

Globular clusters are tightly bound groups of stars that live on the outskirts of galaxies. They make for interesting places of study since usually most of the stars within a particular cluster formed around the same age, so studying different clusters of different ages gives us information about star’s evolutionary paths. Most globular clusters are quite old though, as opposed to open clusters which are usually much younger, and globular clusters are not producing any new stars. Almost every star in a globular cluster is an older star, at least several billion years old. So herein lay the mystery.

In many globular clusters a certain type of star was observed, blue stragglers. Blue stragglers are very massive hot blue stars. Normally, hot massive blue stars are considered young when they are observed because if it is born that hot and massive it will burn out its fuel generally in several million to a few hundred million years. So the problem with finding them in these globular clusters is that since we know the clusters are much older than a few hundred million years these stars should not exist there. So how is it that these stars are where they are and look how they look??

There were two general theories about how these stars are formed. The first involved collisions between stars. You have two stars of medium mass colliding to make one massive star. The other theory was that of stellar cannibalism, in which one star in a binary system feeds of the mass of the other star. Binary systems are just those that contain two stars orbiting around and interacting with each other.

Researchers set out to answer this question by looking at 56 globular clusters. They found that the predicted number of collisions did not match that which was required to give the number of blue stragglers, thus dispelling that theory. They did, however, notice a correlation between the mass contained within the core of the cluster and the number of blue stragglers. It is known that the more massive the core is the higher numbers of binary systems exist within it. Thus they could infer a relationship between number of binary systems and the number of blue stragglers, seeming to support the second theory. This conclusion is also supported by direct observation of the number of binary systems in cluster cores. All of this points toward stellar cannibalism as the explanation. This would not be the only instance of stellar cannibalism in the galaxy. It has been seen many times in binary systems where one star is massive, usually a red giant, and the other is a white dwarf, or already dead star. The smaller white dwarf accretes matter from its larger partner until nuclear burning reignites on the star causing a nova explosion.

The next step for these researchers is to try and find out some information about the original two stars in the binary system, or the parents of the blue straggler. There must be something special about these binary systems that initiates the cannibalism. Are they mostly isolated, or could dynamical interactions between the system and nearby stars be a factor? It’s interesting that we do know a lot about stellar evolution and dynamics but there is always new and interesting ways in which the universe is trying to stump us.

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Balloon Picking up Mysterious Radio Signals

Friday, January 16th, 2009 by Bellatrix

NASA’s most recent balloon trip has found something new and unexplained, don’t you just love when that happens. The ARCADE balloon mission has uncovered a new radio signal with unknown origin, which may be more of an interesting find than the balloons real mission.

The findings come from NASA’s balloon borne instrument known as Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission, or ARCADE. ARCADE was launched in July of 2006 in Palestine Texas. It flew to an altitude of 37km, 120,000 ft, where the atmosphere thins and begins to give way to space. It took data for about 4 hours before parachuting back to Earth. Balloons like this one are used for this reason, they can get above the interference caused by our atmosphere but are much cheaper to launch and build then a full blown satellite.

ARCADE’s mission was to observe and collect radio data from some of the first stars born in our universe. Since these stars are so distance their light is only observable at radio wavelengths. For the instrument to be sensitive enough to pick up this information it had to be cooled, really cooled. It was sent up with 500 gallons of liquid helium to keep it at a frosty 2.5 degrees Celsius above absolute zero. So it was all poised and ready but the data it was sent to collect was lost in a powerful radio signal of unknown origin.

This background radio signal was about 6 times larger than what they had expected to find. It was too strong, or loud, to be coming from the distant stars, and even too loud to be coming from known radio sources like gas from the halo of our galaxy. All galaxies give off some radio noise, usually just a hiss, except for those which are radio loud, usually quasars. But even with all these radio loud galaxies there isn’t enough of them to account for this noise, for the noise to be coming from just galaxies there’d have to be so many radio galaxies they’d be packed in like sardines, one right next to another, which just isn’t the case.

So obviously there’s something that we are missing, something loud making this racket that we don’t even know about; and that’s exciting. This is a great example of why astronomy is so exciting. This routine type mission that was supposed to just give a few details on a particular type of star and then BAM! There’s a mystery with possible far reaching implications. Is this a new object all together? Is it an evolutionary stage of galaxies that we didn’t know about? NASA hasn’t yet mentioned any planned follow up to try and dig deeper into this mystery but I’m sure that it is coming, I mean everyone loves a good mystery.

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