Tag Archives: charon

Charon’s Cracks Formed During Ancient Near-Misses With Other Worlds

Ever since the gargantuan cracks on Plutos moon Charon were first spotted, astronomers have been baffled as to what may have formed them, with explanations ranging from giant impacts to an active, hot mantle.

A new paper, due to be published in the journal Icarus, has come up with an alternative, and arguably more compelling, explanation:Based on a series of computer simulations, it appears that a long history of near-misses by other massive objects, and not plate tectonics, may be responsible for forging mountains and canyons on this distant world.

I was inspired by computer graphics code in how to model the icy moons, Alice Quillen, a professor of physics and astronomy at the University of Rochester and lead author of the study, said in a statement. The inside of the moons is similar to how blood splatter is modeled in games and the outer, icy crust is similar to modeling clothes and how they move.

The computer simulations of the close tidal encounters. Alice Quillen via YouTube

Earth’s Moon may be small, but it’s still sufficiently sizable to be able to generate tides on Earth with its gravitational pull, both at the surface and within the liquid outer core. This mechanism is known as tidal forcing, and the authors of this new study hypothesizedthat this phenomenon may have once acted on the surfaces of icy worlds and moons like Charon when similarlysized worlds drifted close by in the Solar System, although they don’t specify when this would have happened.

The researchers decided to use an N-body simulation, which models objects as having multiple internal regions interconnected by springs. Its commonly used by astrophysicists to model the effect of gravity on planets and stars, but this is the first time it has been applied to a moon.

A massive perturber forming cracks on a Charon-like icy world. Alice Quillen via YouTube

In multiple virtual experiments, simulated icy moons were kept stationary as similar mass objects flew by them, and the team watched as they became deformed.

As it turns out, such close encounters exert enough of a tidal force on the icy moons to cause their surface to fracture in a brittle manner and on surprisingly huge scales. This means that the giant cracks and complex fault structures on the icy moons of Dione and Tethys (of Saturn), Ariel (of Uranus), and Charon (of Pluto) at the very least may be caused by this mechanism.

A close-up of the tectonic belt on Charon. NASA/JHUAPL/SwRI

We know that Earths internal heat escapes through both volcanoes and, significantly, convection currents in the mantle; these move around tectonic plates, which create mountains, faults, canyons, ocean basins, and continents. This process is known as plate tectonics, and its been happening on Earth for at least 3 billion years, but theres little evidence that it has happened anywhere else in the Solar System.

Icy moons like Charon are thought to be too small to still contain any heat left over from their presumably violent formation, so its unlikely that plate tectonics ever managed to effectively operate on them in the same way they did, and still do, on Earth. Perhaps this new study has finally solved the conundrum of where the ginormous alien crevasses come from or, as another recent study suggested, these vast canyons may have instead formed as the icy moon cooled and contracted.

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Read more: http://www.iflscience.com/space/charons-cracks-formed-during-ancient-near-misses-other-worlds

Pluto’s Moons Behave Like Spinning Tops

We know that Pluto is unlike anything we ever imagined, and its family of moons is no exception. Before arriving at the Pluto system, scientists made some predictions about Plutos small moons based on data collected by the Hubble Space Telescope and other observatories. Some were pretty spot on, and others were way off. Lets take a look at what weve learned so far about this incredibly interesting and dynamic system.

The Pluto system is composed of the binary pair of Pluto and its largest moon Charon, with four smaller moons Nix, Styx, Hydra, and Kerberos orbiting the duo. Since Pluto and Charon orbit a common barycenter, its better to think of Pluto and Charon as a pair rather than a planet and a large moon. Prior to its closest approach, data from the Hubble Space Telescope predicted that Plutos small moons orbit in a chaotic fashion.

The vast majority of moons in the Solar System are very well-behaved: orbiting in synchronous rotation and tidally locked with their planet, keeping the same face toward the planet all the time. As the science team analyzes the New Horizons data, we are seeing time and time again that Pluto’s small moons do not play by these rules; they write their own.

During a briefing at the 47th annual meeting for the Division of Planetary Science, Mark Showalter of the SETI Institute said, Weve gone from dots to details in less than 10 years. Its amazing what we have learned so far. Its not chaos in this system, its pandemonium.

New data from the New Horizons spacecraft reveals the small satellites are spinning much faster than first predicted. For example Hydra, the most distant moon, spins a whopping 89 times in one single orbit. Hydra is acting like a typical Kuiper Belt Object, Showalter said. It spins 89 times in one time around Pluto; flaunting everything we know about objects in the Solar System, Hal Weaver, New Horizons project scientist added.

Our first response to this might be to ask why Hydra is spinning so fast, but the better question is Why hasnt it slowed down? The science team doesnt quite understand all the dynamics of the Pluto system yet, but one hypothesis is that Charon exerts a strong torque on the smaller satellites, preventing them from slowing down and settling into a synchronous rotation.

Nix, Plutos innermost, potato-shaped moon could arguably be the most fascinating of the small moons. Spanning 48 kilometers by 32 kilometers (29 miles by 19 miles) roughly the surface area of Los Angeles the surface is void of any boulders or fractures, but we do see a fewrecognizable craters and a few potential craters that we cant quite resolve. The wobbly potato moon also rotates backwards, and even increased its spin rate by as much as 10percent between 2012 and2014.

The small moons of Pluto behave like spinning tops. Credit: Nasa/Youtube

Styx and Kerberos are so small and low mass that its no wonder our predictions for Kerberos were completely off. Originally scientists believed the moon to be darker than the others, but recently returned data from New Horizons shows the tiny moons surface to be just as reflective as the rest.

Images of the small moons indicate that at least two of them Kerberos and Hydra appear to be dual-lobed and could have formed as a result of two different bodies merging together. This suggests that at one time Pluto may have had more moons. Showalter and Alan Stern, New Horizons principal investigator, suspect that the small moons formed during the sameimpact that created Charon.

Scientistscombined data collected from New Horizons with computer models and concluded that an object smaller than Pluto but larger than Charon had to have struck the protoplanet Pluto in order to create the two bodies we see today. The data also indicates this impact had to have taken place a very long time ago, not long after the formation of the original body.

Read more: http://www.iflscience.com/space/plutos-moons-behave-spinning-tops-ke-editing