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.

NASA Plans to Capture Asteroid In Moon’s Orbit

Photo credit: NASA/AMA

Photo credit: NASA/AMA

As part of the Asteroid Redirect Mission (ARM), NASA and cooperative scientists have been searching for a suitable asteroid to capture and redirect into the moon’s orbit for continual research. The ARM spacecraft is proposed to launch in 2019. Once set in orbit, the hands-on examination of the asteroid will begin in the 2020s. The mission has two main focuses: to develop the expertise needed for deep space travel to Mars and beyond, as well as providing an opportunity to test technologies that will keep Earth safe from any possible future asteroid impacts.

There are two concepts set for NASA’s ARM operation: “The first is to fully capture a very small asteroid in open space, and the second is to collect a boulder-sized sample off of a much larger asteroid. Both concepts would require redirecting an asteroid less than 32 feet (10 meters) in size into the moon’s orbit. The agency will choose between these two concepts in late 2014 and further refine the mission’s design.”

Recently a $4.9 million award has been offered for concept studies that will lead to the ARM’s success. Starting in July, a six-month research period will begin that addresses the issues of the mission. During this time the technologies, mechanics and resources needed for the mission will be perfected.

As of now, only nine asteroids have been identified that meet the criteria for possible mission nominees. Using NASA’s Spitzer Space Telescope, the most recent asteroid candidate has been identified. The telescope’s “warm” mission began in 2009 once its coolant ran out as planned, and since then Spitzer has been used for more long term and targeted observations. In particular this makes asteroid observation easier as infrared detection is the best way to study less luminous objects.

The recognition of the latest contending asteroid, named 2011 MD, for possible capture as part of the Asteroid Redirect Mission, was published June 19th, 2014 in the Astrophysical Journal Letters. Lead author of the study, Michael Mommert of Northern Arizona University says, “From its perch up in space, Spitzer can use its heat-sensitive infrared vision to spy asteroids and get better estimates of their sizes.” To be deemed valid, the asteroid must be both the right size and mass, but also the rotation rate must be considered to make its capture feasible.

2011 MD is one of the lucky asteroids that has met all necessary criteria for redirection. It has a diameter of about three to six meters (10-20 feet) with a density similar to water, this suggests that the asteroid is mostly empty space, as solid rock is usually at least three times denser than water. 2011 MD may either be a singular solid rock with a halo of particles surrounding it or a collection of smaller space rocks held in tandem by gravity. Only further observation will conclude indefinitely what its composition is.

The idea of capturing an asteroid and setting it in orbit around the moon is truly exciting! It will be the first time that humans have achieved such a massive cosmic endeavor. Building a stellar environment that fits our research needs almost seems more science fiction that reality; however, if we wish to take humans into deep space it is a necessary leap to make. Not only is the Asteroid Redirect Mission awesome in its concept, it will prove to be incredibly valuable in a scientific standpoint as well. John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, says, “Observing these elusive remnants that may date from the formation of our solar system as they come close to Earth, is expanding our understanding of our world and the space it resides in.”


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This article was originally written for and published by From Quarks to Quasars.