A Distant Glimpse of Uranus

JPL PIA17178 (detail)Last month, Cassini got its first-ever glimpse of Uranus:

NASA’s Cassini spacecraft has captured its first-ever image of the pale blue ice-giant planet Uranus in the distance beyond Saturn’s rings.

The planets Uranus and Neptune are sometimes referred to as “ice giants” to distinguish them from their larger siblings, Jupiter and Saturn, the classic “gas giants.” The moniker derives from the fact that a comparatively large part of the planets’ composition consists of water, ammonia and methane, which are typically frozen as ices in the cold depths of the outer solar system. Jupiter and Saturn are made almost entirely of hydrogen and helium, with smaller percentages of these ices.

When this view was obtained, Uranus was nearly on the opposite side of the sun as seen from Saturn, at a distance of approximately 28.6 astronomical units from Cassini and Saturn. An astronomical unit is the average distance from Earth to the sun, equal to 93 million miles (150 million kilometers). At their closest, the two planets approach to within about 10 astronomical units of each other.

Just to be clear, all those AUs add up to just under 4.3 billion kilometers (2.66b miles).

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Dyches, Preston and Steve Mullns. “Cassini Spies the Ice-Giant Planet Uranus”. Jet Propulsion Laboratory. May 1, 2014.

NASA/JPL-Caltech/Space Science Institute. “PIA17178: Blue Orb on the Horizon”. Photojournal. May 1, 2014.

Herschel: Water at Ceres

What’s that? You never met Herschel?

Via ESA:

ESA’s Herschel space observatory has discovered water vapour around Ceres, the first unambiguous detection of water vapour around an object in the asteroid belt.

Water!With a diameter of 950 km, Ceres is the largest object in the asteroid belt, which lies between the orbits of Mars and Jupiter. But unlike most asteroids, Ceres is almost spherical and belongs to the category of ‘dwarf planets’, which also includes Pluto ….

…. [U]sing the HIFI instrument on Herschel to study Ceres, scientists have collected data that point to water vapour being emitted from the icy world’s surface.

“This is the first time that water has been detected in the asteroid belt, and provides proof that Ceres has an icy surface and an atmosphere,” says Michael Küppers of ESA’s European Space Astronomy Centre in Spain, lead author of the paper published in Nature.

Although Herschel was not able to make a resolved image of Ceres, the astronomers were able to derive the distribution of water sources on the surface by observing variations in the water signal during the dwarf planet’s 9-hour rotation period. Almost all of the water vapour was seen to be coming from just two spots on the surface.

“We estimate that approximately 6 kg of water vapour is being produced per second, requiring only a tiny fraction of Ceres to be covered by water ice, which links nicely to the two localised surface features we have observed,” says Laurence O’Rourke, Principal Investigator for the Herschel asteroid and comet observation programme called MACH-11, and second author on the Nature paper.

And, really, what can you say? Good show, Herschel. Congratulations, ESA. And thank you. That is really, really cool.

Herschel is named for the guy who discovered Uranus; William Herschel also identified infrared radiation over two hundred years ago. This latest announcement is one of the satellite’s last dramatic gifts; Herschel ran its course, with final commands sent in June, 2013.

It was certainly a good run. And there are probably myriad little gifts remaining to be discovered in the data.

Talk about a show. Water at Ceres. Makes as much sense as anything else, to be certain, but it is also good to know.

Linkadelic Mess

Molloy, 'Burning Cotton Candy' (detail)
Given that year-end lists are something of a useless cliché, we figure it works just as well to do a junkpile and clear out a bunch of links waiting for some more useful deployment than sitting in a badly-punned directory (URLenmeyer) on the desktop. Thus, in no particular order:pH scale

Timestacking.

• Why certain Chinese cat fossils are so fascinating.

Synaptogenesis is a word you will start hearing more often in the near future.

• Sure, it’s a bit old, but A Citizen’s Guide to Understanding and Monitoring Lakes and Streams, from the Washington Department of Ecology, is still relevant.

• There really is a holy grail for dystopic, embittered, supervillainous math geeks.

• Suffice to say, the link file for this one was actually a bad casserole joke. No, really.

• Celebrate the saola, a Vietnamese ox confirmed to still exist after fifteen years out of sight.

• We all heard the cool news about India shooting for Mars?

• The tortoise and the Lego, that’s all you need to know.

• Dinosaurs are human, too. Er, I mean … ah … right. Something about a clumsy dinosaur.

• Apparently, the Milky Way wobbles and flutters. (If you like the technical stuff, the arXiv file is available.)

Ultraviolet … Imaging … Spectrograph; maybe not a band name, but certainly worthy of being an album cover. Vinyl. Twelve inch.

Spiders. Might as well get used to ’em.

• Have you met Juno?

• Ice, water, steam … how about plasma? And no, plasma water is not a sports drink … yet.

• Here there be monsters.Uranus Trojan Lagrange

Uranus Trojan Lagrange is not a band name. It’s something even cooler.

• Then again, Martian eclipse would be a good band name, too.

xkcd on ice.

Teller talks Tim’s Vermeer.

• Various processes more complicated than explanations are worth keep bringing to mind an old episode of Radiolab, about laughter.

Detail of PIA050760