Monthly Archives: June 2015

astronomy, charon, New Horizons mission, Pluto

Announcing Charon’s Dark Pole

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What’s Causing THAT?

These recent images show the discovery of significant surface details on Pluto’s largest moon, Charon. They were taken by the New Horizons Long Range Reconnaissance Imager (LORRI) on June 18, 2015. The image on the left is the original image, displayed at four times the native LORRI image size. After applying a technique that sharpens an image (called “deconvolution”), details become visible on Charon, including a distinct dark pole. Deconvolution can occasionally introduce “false” details, so the finest details in these pictures will need to be confirmed by images taken from closer range in the next few weeks. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

As the New Horizons spacecraft gets closer to Pluto, we are seeing more detailed images of this world and its companion, Charon. The latest ones, taken with the LORRI instrument onboard the spacecraft, show what looks like a darkened pole on Charon, a somewhat lighter region below it, and some bright regions along the limb. “Fascinating” as Mr. Spock would say. But, what is happening at Charon to make it look like that? The final answer is a couple of weeks away, so let’s talk about how we figure out what’s happening at a world (planet, dwarf planet, moon, asteroid, or comet) from images of it.

An artist’s conception of Charon (with Pluto in the background). The plumes and brighter spots depicted on Charon’s “left side” are thought to be created as water (with some ammonia hydrate mixed in) “erupts” from deep beneath the surface. The material sprays out through cracks in the icy crust, immediately freezes and snows crystalline ice down onto the surface, creating a water-ammonia hydrate ice field. Such fields were detected and studied using the near-infrared imager on Gemini North. (This composite image includes Pluto and Charon models (enhanced), courtesy of Software Bisque. www.seeker3d.com, with plumes and ice fields added by Mark C. Petersen, Loch Ness Productions. Star field from DigitalSky 2, courtesy Sky-Skan, Inc.)

As in all other aspects of planetary science, you have to look for processes on the world you’re studying to understand how they affect the surface of that place. For example, if you were approaching Earth and were still quite a ways away as you came in to assume a standard orbit (Mr. Sulu), you’d likely notice the poles, the bluish color, and the darker areas that indicate land masses. The existence of ice at the poles tells you something about the climate and temperature in those regions. The bluish water in a liquid state tells you that conditions are good enough to permit liquid water. And, the land masses have many messages of their own, from the signatures of volcanoes to the ongoing (and long-term) deformation of the surface due to plate tectonics. What you see on Earth, even at the most cursory level — and at Pluto and Charon — are all caused by complex interactions comprising chemical reactions, atmospheric mixing, and actions going on below the surface.

So, with that in mind, what’s going on at Charon? I wish I could tell you for sure. But, it looks really, really interesting! Now that we’re seeing a great variety of surface features (or, as the scientists call it, “terrain types”) it’s a hint that Charon is not just a frozen dead world. A dark terrain could indicate some sort of chemical interaction as sunlight hits specific ices on the surface. That normally happens with methane-rich ice, which Charon doesn’t appear to have much (if any) of. Instead, it has been measured to be mostly water and nitrogen ice.

However, I suspect there’s more going on at Charon than meets the eye.

A few years ago, we created a graphic “approximation” of Charon for a project with Gemini Observatory. We had to guess at what the surface looked like. You can see that, even in 2007, we had an idea that there’d be darker areas on an already darkish object. The real interesting bit was that astronomers using Gemini telescope had spotted what looked like evidence for geyser-like activity on Charon. I will be really interested to see if New Horizons finds that same evidence and confirms such activity. If it does, then we’re looking at a dynamic world with an interior that is forcing mixtures of ammonia hydrates (ammonia mixed with water) and water crystals onto the surface.  And, THAT’s cool.

I don’t know why Charon has a dark pole, yet. I suspect that the New Horizons mission team members don’t YET know for sure. They’re likely going through all the ideas en masse, and once they have more data, we’ll all know what’s ticking inside this little world.

astronomy

Planetary Exploration Rules!

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Mapping the Solar System Continues…

Okay, so I have Pluto on the brain. I admit it.  New Horizons is the last probe to visit a world we haven’t yet visited, so it’s really big news. It’s exciting to think that all our preconceived “views” of Pluto will get blown away just three weeks away from close flyby of this dwarf planet and its moons. Heck, they’re getting blown away each time the folks on the mission issue another image.

But, there are other cool stories going on right now, so let’s spread around a little planetary mission love!

The mysterious glowing white dots of Ceres. What are they? Courtesy NASA/DAWN mission

First of all, the Dawn mission at Ceres keeps cranking out the great images of that dwarf planet. It’s mapping Ceres at high resolution, and on each orbit, it picks up more details of the surface.

The bright white dots that have so intrigued everybody are still…intriguing everybody. It’s not clear why they exist and what they are, but they have the planetary scientists considering many possibilities. Ice and/or salt deposits are two of the many suggestions about what they are. How they got there is still a mystery.

Craters, sunken “graben-like” areas, what looks like a cliff, and a pyramid-shaped mountain also grace Ceres’s surface. NASA/DAWN msision

What else has Dawn seen? Not surprisingly,  for a world without an atmosphere and orbiting in the Asteroid Belt, there are many craters. We also see long sinuous lines that could be cracks, and in one area, a pyramid-shaped mountain that rises up about 5 km (3 miles) above the surface. And, it looks like there are more white spots scattered around the rest of the surface, too. All in all, Ceres is giving us quite a show, and the mapping has only just begun!

The other story that caught my eye this past week is the evidence of active volcanoes on Venus. Now, we’ve known for a long time that Venus is a volcanic world, and studies of its atmosphere have telltale signs of volcanic eruptions. But, no one has ever seen an eruption there because of the heavy, dense cloud cover that obscures our view of the surface.

Thermal (heat) mapping of the Venus surface show hot spots in the region of a volcano called Ozza Mons. Courtesy Ivanov/Head/Dickson/Brown University.

Astronomers spotted some interesting data in observations made by the European Space Agency’s Venus Express mission and thermal (heat) images made by the spacecraft’s Venus Monitoring Camera. It recorded some temperature spikes that just happened to coincide with known hot spots on the planet’s surface. Those hotspots flared up and then slowly faded down, in a manner very similar to what an Earth-bound volcano does when it erupts a lot of material for a while and then slows down. The planetary scientists took this as strong evidence that Venus volcanically active now. That also means that it’s active in its interior, too.

The news from Dawn, New Horizons, Venus Express, as well as Cassini and the swarm of probes at Mars is certainly extending our golden age of planetary exploration. And, now that NASA has committed to a mission to Europa, it looks like that age will continue. Revel in it folks! There are only a few times in history when so much has been discovered on behalf of all of us by our scientist friends and neighbors!