OUT OF THIS WORLD | Earth, Space And The Stuff In Between - a daily journey through weather, space and science with meteorologist/science writer Scott Sutherland

Winter is coming for Titan, and it's unleashing a monster

Find Your Forecast Search for a location

Scott Sutherland

Meteorologist/Science Writer

Wednesday, November 11, 2015, 1:45 PM - A monstrous polar vortex forming on Saturn's Titan. Towering ice volcanoes and oddly spinning moons for Pluto. A meteoroid shower for Mercury. This week's What's Up In Space is a cornucopia of solar system news from the American Astronomical Society's 2015 Meeting of the Division of Planetary Sciences!

Titan's polar vortex turning into a 'monster'

NASA's Cassini spacecraft has returned some incredible images as it orbits around the ringed planet, Saturn, including a recent closest-ever pass over icy Enceladus, but this newly-released image of Titan may be one of the best yet.



A view of Titan's south polar region from 2013, revealing the immense polar vortex cloud that is forming there. Credit: NASA/JPL-Caltech/Space Science Institute

During each of Saturn's years, the planet and its moons go through seasonal transitions, just like we see here on Earth. When Cassini arrived at Saturn in 2004, it was mid-winter for the northern hemisphere of the system. Now, winter is coming for the southern hemisphere, and the pictures Cassini has been sending back are revealing a monstrous cloud forming in the moon's south polar vortex.

The newly released image above is a wide-angle shot from 2013, showing the extent of the immense cloud, while a close-up view from 2012 (shown to the right) reveals the fine details at the apex of the swirling vortex.



Credit: NASA/JPL-Caltech/Space Science Institute

According to NASA, researchers examining the 2012 view found that the cloud reached as high as 300 km into the sky, and was formed as chemical droplets sublimated out of the air sinking over the south pole. Looking at subsequent data gathered by Cassini's Composite Infrared Spectrometer (CIRS), though, they found that there was a much larger cloud directly beneath it - a wispy fog-like structure reaching as high as 200 km above the surface and very likely flat on the top.

"When we looked at the infrared data, this ice cloud stood out like nothing we’ve ever seen before," said Carrie Anderson, a planetary scientist at NASA’s Goddard Space Flight Center, who presented the team's findings at DPS15 this week. "It practically smacked us in the face."

Data collected by Cassini shortly after its arrival showed the presence of a north polar vortex at the time, however these findings definitely tell us something new about Titan's seasonal transitions.

"The opportunity to see the early stages of winter on Titan is very exciting," said Robert Samuelson, a research scientist at NASA Goddard who worked with Anderson. "Everything we are finding at the south pole tells us that the onset of southern winter is much more severe than the late stages of Titan's northern winter."

Pluto is the solar system's rising 'star'

Back in July, just a few days after the New Horizons spacecraft flew past Pluto and its moons, mission principle investigator Alan Stern said: "I'm a little biased, but I think the solar system saved the best for last."

Based on what we're getting back from the mission, it seems truer words could not have been spoken.

Ice volcanoes?

When the surface of Pluto was imaged for the first time, there was speculation that some of the numerous mountains spotted there could be what are known as cryovolcanoes - volcanoes that spew water vapour, methane and other volatiles instead of lava.

While the science team was understandably cautious, and possibly even skeptical, at the time, based on the latest images, it seems that's just what they've found.



3.2 km-high "Wright Mons" - located to the south of Pluto's Sputnik Planum - both in black-and-white (left) and false-colour elevation (right) images. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

"These are big mountains with a large hole in their summit, and on Earth that generally means one thing - a volcano," Oliver White, a New Horizons postdoctoral researcher at NASA’s Ames Research Center, said in a statement. "If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath. The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have traveled down from the summit region and onto the plains beyond, but why they are hummocky, and what they are made of, we don't yet know."

Wright Mons, shown above, is just one example of what may be a Pluto cryovolcano. Piccard Mons, just to the south of Wright Mons and standing over 5.5 km high, could be a second one.

Spinning, dancing moons

New Horizons managed to capture all five of Pluto's moons, right down to tiny Kerberos, and based on observations and simulations, it seems that other than Charon, which is tidally-locked to Pluto, the other four have some pretty crazy antics as they orbit around the system.

In the video below, keep an eye on Hydra, the outermost object in the Pluto-Charon system, and how fast it spins.

"Pluto's moons behave like spinning tops," New Horizons co-investigator Mark Showalter, of the SETI Institute, said in a NASA statement.

Based on images of these four smaller moons, in some cases, the explanation for this strange spinning is fairly apparent.



Credits: NASA/JHUAPL/SwRI

The gravitational dance between Pluto and Charon is a definite influence on this spinning, due to the uneven "pull" exerted on them as they go around the binary planet. However, their spinning could also be partly due to the fact that they are the result of ancient mergers between smaller objects. The circles overlaying Kerberos and Hydra, in the image above, show how this possibility is particularly obvious in their structure.

"It's hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the solar system," New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, said in a NASA statement. "Moreover, I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding. To have them all is simply incredible."

Mercury pelted by a comet



Artist's conception of Mercury's meteoroid shower.

Credit: NASA Goddard

Here on Earth, we see numerous meteor showers every year, as our planet passes through trails of debris left behind by passing comets. It stands to reason that other planets are bound to encounter these trails as well, and a team of researchers have found that Mercury, the closest planet to the Sun, experiences an annual shower of its own.

They discovered this using data from NASA's MErcury Surface Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, which found a recurring peak in the concentration of calcium in the planet's tenuous atmosphere, which showed up at roughly the same time during each of Mercury's 88-day-long years.

With the knowledge that Mercury's atmosphere is at least partly generated by impacts with particles from the cloud of "zodiacal dust" that exists between the Sun and Jupiter, they sought out a specific source for this recurring calcium peak. One clue that led the researchers to the source was the fact that the peak in calcium concentration didn't match when they expected it would occur. Given the concentration of zodiacal dust, the greatest number of impacts (and thus the largest amount of calcium being kicked up into the atmosphere) should happen just before Mercury reaches its closest point to the Sun. However, the calcium peak was seen after it passed that point.

This pattern of its occurrence traced it to when Mercury passes through the debris stream of Comet Encke - the same object that's responsible for the Taurid meteor showers we see in our skies from late October to the end of November.

Even then, the match wasn't perfect. The timing was off by roughly a week. However, astronomers have already determined that this ancient comet's debris stream is so spread out near Earth's orbit that it has actually split into two. Thus, it generates both the northern and southern Taurid meteor showers, which appear to originate from two slightly different points in the night sky. The evolution of Encke's debris stream over time in the vicinity of Mercury could account for the mismatched timing.

"We already knew that impacts were important in producing exospheres," Dr. Rosemary Killen, a planetary scientist at NASA’s Goddard Space Flight Center, said in a statement. "What we did not know was the relative importance of comet streams over zodiacal dust. Apparently, comet streams can have a huge, but periodic, effect."

Why is this Mercury shower called a meteoroid shower instead of a meteor shower? Meteors are the bright streaks of light caused as meteoroids encounter the atmosphere of a planet. The tiny bits of dust and ice are moving so quickly that they compress the air in their path, heating that air up until it glows. Mercury's atmosphere is far too thin to be compressed that much, so the shower doesn't produce any meteors.

Find more about what's going on at the American Astronomical Society's 2015 Meeting of the Division of Planetary Sciences by following the hashtag #DPS15 on Twitter.

Sources: NASA | JHUAPL | NASA Goddard



