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Eppur Si Muove: Galileo’s Big Night

Jupiter and its four largest “Galilean” moons photographed on April 16, 2016. © Jason Major

On this night in 1610 the Pisan astronomer Galileo Galilei looked up at a bright Jupiter at opposition through his handmade telescope and noted three little “stars” next to it, piquing his natural scientific curiosity. Further observations over the next few nights showed that the planet wasn’t moving relative to the little “stars” as it would have if they were indeed background stars. In fact the smaller objects (of which he soon saw four) were moving along with Jupiter, each in its own little path. He realized that the little objects weren’t stars at all but rather moons orbiting the giant planet—and, most importantly, not the Earth. This revelation helped change our entire view of the Solar System… and caused no end of trouble for Galileo as the Church didn’t appreciate a restructuring of their conveniently Earth-centered Universe. But it also opened the door for later discoveries of many more moons around other planets.

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Juno and JEDI Deliver New Discoveries About Jupiter

JunoCam image of Jupiter’s Great Red Spot from July 11, 2017, processed by Gerald Eichstadt and edited by Jason Major.

Saturn has its rings, Mars has its rusty landscape, Earth has its whales, water, and wi-fi…and Jupiter has its Great Red Spot. The giant gas planet’s enormous orange storm—once over twice the diameter of Earth but today “only” about 1.3 times as wide—is one of the most distinctive planetary features in our Solar System. It’s so well-known that even young children are sure to include its orangey oval when drawing Jupiter!

Jupiter imaged by Hubble on 4-3-17. NASA, ESA, and A. Simon (GSFC).

But as famous as it is, there’s a lot we still don’t know about Jupiter’s giant storm. NASA’s Juno spacecraft, launched in August 2011, has now been orbiting Jupiter since July 4, 2016 and has been using its suite of science instruments to investigate the planet’s complex atmosphere like never before possible. Thanks to Juno, for the first time scientists are able to “see” deep below Jupiter’s dense clouds (in microwave wavelengths, that is) and find out what’s happening inside the GRS. What they’ve discovered is a storm hundreds of miles deep with a hot base that powers its winds.

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We May Have Just Been Visited By An Interstellar Comet

“This object came from outside our solar system.”
— Rob Weryk, postdoctoral researcher at University of Hawaii’s Institute for Astronomy

Diagram of the path of C/2017 U1 PanSTARRS (now A/2017 U1), a possible interstellar comet (or asteroid) spotted on Oct. 18, 2017. (NASA/JPL)

On October 14, 2017, what appears to be a comet (er, make that asteroid…read more below) sped past Earth at a distance of about 15 million miles after swinging around the Sun. It had come within 23.4 million miles of our home star over a month earlier on Sept. 9, and in fact wasn’t spotted by astronomers until Oct. 18—four days after its closest pass by us.

Further observations showed that the approximately 525-foot-wide object (an estimate based on its reflectivity) first approached traveling 16 miles a second from the direction of the constellation Lyra—quite a high angle from the plane of the rest of the Solar System—and is on a hyperbolic trajectory, moving quickly enough both in- and outbound along its course to permanently escape the Sun’s gravity unlike any other comet asteroid ever observed.

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How To Make A Moon: New Research Is Raising Questions On Our Moon’s Birth

New research is raising questions about the currently-accepted “Giant Impact” hypothesis of the Moon’s formation. (NASA image)

There are a lot of moons in our solar system—175 major planet satellites, and three times that if you count every natural satellite of every known object (like asteroids)—but among them our own capital-M Moon is in many ways unique. At a full quarter the size of Earth, only Pluto has a moon so near in size to itself, and unlike the swarms of icy worlds orbiting the gas giants the Moon is oddly very similar in composition to Earth…so similar, in fact, that it’s been casting increased doubt on the accuracy of the best-accepted model of the Moon’s formation, namely the Giant Impact Hypothesis.

Suggested in 1975 by planetary scientists William K. Hartmann and Don Davis, the model claims that the Moon was created 4.5 billion years ago when a Mars-sized world that’s been named Theia impacted the newly-formed Earth, blasting a chunk of molten material out into orbit that solidified to form the Moon. The model is based on a lot of science and answers a lot of questions, but not all—including a key issue of why the Moon today appears compositionally identical to Earth and not a mixture of Earth and a completely different planet.

As advanced computer measurement and modeling capabilities have increased a new wave of researchers are tackling the conundrum of the Moon’s origins, and a few new scenarios are coming to light. While ancient impacts are still involved, the question is now how many? With what kind of world(s)? And what exactly happened after the event?

“In the past five years, a bombardment of studies has exposed a problem: The canonical giant-impact hypothesis rests on assumptions that do not match the evidence. If Theia hit Earth and later formed the moon, the moon should be made of Theia-type material. But the moon does not look like Theia—or like Mars, for that matter. Down to its atoms, it looks almost exactly like Earth.”

Read the full story by Rebecca Boyle in The Atlantic here: The Moon’s Origin Story Is in Crisis

This Toxic Compound on Titan Could Support Life “Not as We Know It”

Illustration of a sunrise over a liquid methane lake on Titan. © Ron Miller. All rights reserved.

Saturn’s largest moon Titan is often called an analogy to early Earth, with its thick, chemical-rich atmosphere and widespread system of flowing rivers and north polar lakes. But located almost a billion miles away from the Sun, everything on Titan is shifted into a completely different—and frigid—level of existence from that found on Earth. With surface temperatures of 300 degrees below zero F, the lakes are filled with liquid methane and what’s life-giving water here is literally solid rock there. Even the rain on Titan falls as oversized drops of ethane.

But even in this extreme cryo-environment it’s possible that life may right now exist…life relying on an entirely different chemistry than what’s possible on our planet.

Recently scientists have identified a molecule on Titan called vinyl cyanide, or acrylonitrile. To Earthly life acrylonitrile is toxic and carcinogenic; luckily for us it isn’t naturally-occurring here. But on Titan it is and apparently in quantity; it’s possible that vinyl cyanide, raining down from Titan’s atmosphere into its vast hydrocarbon lakes, could even help form methane-based cell structures in much the same way phospholipids do here.

The molecule (C2H3CN) has the ability to form membranes and, if found in liquid pools of hydrocarbons on Titan’s surface, it could form a kind of lipid-based cell membrane analog of living organisms on Earth. In other words, this molecule could stew in primordial pools of hydrocarbons and arrange itself in such a way to create a “protocell” that is “stable and flexible in liquid methane,” said Jonathan Lunine (Cornell University) who, in 2015, was a member of the team who modeled vinyl cyanide and found that it might form cell membranes.

Further evidence of life “not as we know it?” Read more on Ian O’Neill’s Astroengine blog here: Vinyl Cyanide Confirmed: Weird Form of Alien Life May Be Possible on Saturn’s Moon Titan and in a Gizmodo article by Maddie Stone here: Potential Building Block of Alien Life Spotted in Titan’s Atmosphere

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