space

Origin of Enceladus’ 101 Geysers Revealed

Jets of liquid water can be seen shooting out of Enceladus' icy surface. They are seen "spewing 200kg of water vapour and ice particles into space each second – enough to fill an Olympic swimming pool every few hours" (Cosmos) Credit: NASA/JPL

Jets of liquid water can be seen “spewing 200kg of water vapour and ice particles into space each second – enough to fill an Olympic swimming pool every few hours” (Cosmos). Image Credit: NASA/JPL

Using data provided by the Cassini-Huygens spacecraft scientists have pinpointed 101 geysers on Enceladus, one of Saturn’s icy moons. Issued in a press release by NASA, July 28th, 2014, the findings are helping scientists understand the geological processes that may allow for liquid water to exist on the moon’s surface.

The first geysers were spotted nearly ten years ago on the moon. Since then scientists have been able to resolve not only where they were being formed, but also how. Early hypothesis’ suggested that pressure built up by the flexing of the small moon’s surface was heating ice into vapor; once an enough tidal friction melted an opening on the surface, a geyser would erupt allowing the pressure to be released.

Using Cassini scientists were able to triangulate the locations of 101 fountains and have found the south pole of the moon to be a breeding ground for the geysers. Tiger stripe fractures run across the terrain of Enceladus in this area. Measurements taken over the last seven years have indicated that the geysers are erupting from hot spots along these striped fractures. This is a great clue for the scientists because it offers a possible origin for the water that spews from these vents.

Scientists have been able to correlate the intensity of the jets to thermal radiation as well as tidal stressors. It was apparent that higher temperatures were associated with the vents, however, it was unknown if increased temperatures were causing the geysers or vice versa. By analyzing high-resolution data gathered by Cassini’s heat-sensing technology in 2010 and 2012, the scientists could say definitively which came first, the chicken or the egg. In this case, it is the geysers that are causing the increased temperatures on the surface of Enceladus. Carolyn Porco, leader of the Cassini image team said in a report published in the Astronomical Journal, “[The results] told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

Image Credit: NASA/JPL-Caltech/Space Science Institute

Image Credit: NASA/JPL-Caltech/Space Science Institute

Scientists now believe that the underground sea that resides on the moon is the most plausible source of these watery fountains. “They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water.” Enceladus’ sea is believed to be nearly 10 kilometers deep, covered by 30-40 kilometers of ice near its south pole. It is still unclear why much of the moon’s water appears to be concentrated in this region. Porco had long suspected that Enceladus was releasing heat from within. Small silica particles have been spotted in the plumes, this combined with the newest evidence of deep channels connecting the moon’s surface with its underground sea gives scientists more hope of possibly finding life here.

In an article published in the journal Nature, in April, 2014, it states, “At the bottom of the Enceladus ocean, the water presumably comes in contact with the moon’s rocky core. “What matters about the new result is they say they have evidence for the ocean contacting rock,” says Christopher McKay, an astrobiologist at NASA’s Ames Research Center in Moffett Field, California. “That’s very important because pure water is not interesting biologically — the water needs to interact with rock in order to put in the stuff that’s useful for life.”

Hydrothermal vents on Earth act as transmitters of heat and chemicals from within the planet’s interior and they have been found to harbor the most extreme forms of life. Only further research will tell if similar underwater outlets are heating Enceladus, and whether or not biological life may be hiding there.

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Cleaning the Cosmos with Space Harpoons

Infograph by NASA's Jet Propulsion Laboratory

Infograph by NASA’s Jet Propulsion Laboratory

 

There are over 17,000 individual pieces of human-made space debris, floating without regard, in Earth’s low orbit. These are the discarded remnants of nearly sixty years of space exploration. Space junk consists of anything from spent fuel cells to battery packs. The nearly twenty thousand pieces of trash left in space accounts for items that are large enough to be tracked and cataloged, objects roughly the size of a coffee cup. If scientists account for even smaller debris, bits and pieces 1 cm or larger: flecks of paint, nuts, bolts, screws, etcetera, and the number is expected to exceed 300,000 (NASA).

Image Credit: ESA

Image Credit: ESA

It’s becoming apparent that humans are no better at keeping debris out of space, than we are at keeping rubbish out of the oceans. The difference is trash in the oceans contributes to global pollution, disturbances in ecosystems, and the destruction of species unable to adapt our insatiable thirst for development and technology. The junk we have accumulated in space, on the other hand, has the potential to anchor us to this ever-polluted Earth indefinitely; creating an exponentially growing shield of debris that could make future space travel obsolete.

In addition to possibly halting our route to the universe, space garbage posses danger to any number of beneficial satellites that also inhabit low Earth orbit. Without such machines, much of the technologies we have grown accustom to today would cease to function. We use satellites for tracking weather and making predictions, navigation while driving, for communication, and scientific research. The potential for collisions between space debris and any one of these satellites is a viable concern.

Harpooning System. Image Source: ESA

Harpooning System. Image Source: ESA

SPACE HARPOONS — SPEARING THE BEASTS:

This why the European Space Agency has announced they hope to start the cosmic clean up as soon as 2021. The e.DeOrbit mission is part of the ESA’s Clean Space Initiative; it’s main task: to hunt down renegade space debris in key orbiting regions and safely remove it. A variety of suggestions have been made for how to capture the wreckage. Nets and mechanical arms have been popular choices, and may very well aid in tidying up space; however, recent ESA research has shown promising results using harpoon technology.

Preliminary investigations, by Airbus Defense and Space, regarding harpoon technology and other waste removal concepts have already taken place. Paying homage to an ancient hunting technique, scientists hope to shoot out a harpoon attached to a tether, pierce the debris and reel it back in.

A prototype harpoon was projected into representative satellite material to assess its penetration, its strength as the target is pulled close and the generation of additional fragments that might threaten the e.DeOrbit satellite.

Scientists have already assessed a mock-up version of the technology. It was shot into demonstrative space junk to test how well it can puncture the material, whether it was powerful enough to reel it back in, and most importantly, that it doesn’t create more fragments in its wake.

 “As a next step, ESA plans to build and test a prototype ‘breadboard’ version in the hope of adopting the harpoon and its ejection mechanism for the mission.The project will investigate all three stages of harpooning through computer models, analysis and experiments, leading to a full hardware demonstration.”

[Reference: ESA]

It is yet to be seen which means of trash removal will be the most beneficial. It may prove necessary for us to employ a variety of methods dependent on the size of the material in question.

Check out From Quarks to Quasars for more awesome space articles!

Segue 1: Time Capsule of an Ancient Universe

There’s something fascinating about Segue 1, a galaxy first noticed in 2006 by the Sloan Digital Sky Survey. From the beginning, this patch of sky was puzzling to astronomers because despite it being only 75,000 light years away, the stars were extremely dim. A year later in 2007, Dr. Marla Geha of Yale University looked at this section of space in more detail. Her team concluded that Segue 1 is among the oldest galaxies in the universe! The stars contained within are billions upon billions of years old, harking back the first moments in history when galaxies first emerged.

Segue 1, which is situated in the constellation Leo, is exclusive for a couple reasons. First off, it only contains around a thousand stars, so it’s pretty puny dwarf galaxy. In comparison, our Milky Way has far more stars, around 400 billion. Segue 1, on the other hand, is mostly comprised of dark matter. Its overall mass is thousands of times greater than what can be accounted for based on stars alone! It isn’t just the lack of stars that makes Segue 1 so alluring though, or its abundance of dark matter; what really sets it apart from other dwarf galaxies is its chemical composition.

Both images of Segue 1show that the galaxy is so barren, it’s hard to classify it as one (Image Credit: MIT)

Both images of Segue 1show that the galaxy is so barren, it’s hard to classify it as one (Image Credit: MIT)

THE CAUSALITIES OF THE RED-GIANT:

In an article published in the Astrophysical Journal titled, “Segue 1: An Unevolved Fossil Galaxy From the Early Universe”(arXiv version), a team of astronomers – led by Anna Frebel, from the Department of Physics at MIT – detail the unique attributes of this ancient collection of stars. With the help of the Magellan Telescope in Chile and the Keck Observatory in Hawaii, the team members were able to study a few of the brightest red giants in the galaxy.

By reading the spectrum of light emitted from the red giants, it was concluded that there is an extreme lack of metallic elements present within the galaxy. This finding was perplexing because of the galaxy’s age. Surely it should have had enough time to produce an abundance of heavy elements, however, very few were found.

Nebulae are the breeding grounds of stellar evolution. Clouds of gas and dust coalesce with the help of gravity to eventually start the fusion process of hydrogen into helium. After a billion or so years of fusion, the star generally explodes as a supernova; spewing its material out into the universe to start the process over again. However, due to the lack of heavy elements, Frebel and her team have concluded that the stars within this galaxy never matured.

FROM A SEED BLOOMS A GARDEN:

Due to the properties of fusion, heavy elements are usually formed in stars that are older and more massive. Stellar furnaces convert simple elements into heavier ones by fusing atomic nuclei; eventually it maxes out when the core begins to fuse into iron. The overall chemical fingerprint of Segue 1 shows it contains about 1/2,500th of the iron our Sun does, only a few dozen such stars have ever been discovered that fit this criteria to a point.

Dwarf galaxies are common and provide value because they don’t experience the same extensive evolution as their larger counterparts do. In other words, they don’t go through multiple generations of supernovae/nebulae cycles. Due to this, they are considered relics of earlier times and hold more clues to the state of the universe during those points than modern renderings ever could. These small galaxies may even influence the formation of larger ones.

For Segue 1 specifically, it is believed that the elements with a weight higher than helium are the result of a limited amount of supernova explosions. Until we find more galaxies like it. we can only speculate as to why its development stalled. What we do know is that Segue 1 was born near the beginning of time and only progressed for a few generations; its like looking into a time capsule of the early universe!


 

This article was written by me, and originally published by From Quarks to Quasars, May 17, 2004.