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
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
Comets are the icy remnants left over from the formation of the Solar System. They circle the Sun in highly elliptical orbits that can range in length from several years to several million years, depending on their origin, and while they are usually quiet and dark when they get close enough to the Sun they are briefly heated enough to melt—technically sublimate—some of their frozen material, forming a cloud of gas and dust and a long tail sometimes big and bright enough to be visible from Earth.
But for the majority of their travels most comets are dark and difficult to spot, especially those originating from the Oort Cloud, an enormous spherical zone of icy debris surrounding our Solar System 186 billion miles away. Now, using infrared data from NASA’s WISE spacecraft, researchers have concluded that there are many more so-called “long period” comets visiting from the Oort Cloud than previously suspected—at least seven times more—and that they’re larger than we thought, too…many over half a mile across.
Today after almost 11 months in orbit the Juno team revealed the first scientific findings of the mission to the public via a NASA teleconference, giving us our first peek at the inner workings of Jupiter and how much of a surprise our Solar System’s largest planet is proving to be…which of course is quite fitting, as the spacecraft is named after the wife of Jupiter who could see through her mischievous husband’s veiling clouds.
“The new science results from Juno really are our first look close-up at how Jupiter works,” said Scott Bolton, principal investigator for the Juno mission. “For the first time we’re looking inside of Jupiter at the interior, and what we’re seeing is it doesn’t look at all like what we predicted.”
Ok, technically it’s not a new moon as it’s probably several billion years old but we didn’t know about it before, so it’s new to us! A team of researchers has just announced the discovery of a 150- to 250-mile-wide moon orbiting a dwarf planet in the Kuiper Belt named 2007 OR10. This distant, icy world is only 950 miles wide itself but it’s still the third largest dwarf planet, ranking behind Pluto and Eris in size.
The existence of the moon was first hinted at in observations by NASA’s Kepler telescope, which showed 2007 OR10 to be rotating suspiciously slowly for a KBO—45 hours as compared to a more typical under 24. After reviewing earlier Hubble observations of the object a moon was positively identified.
This discovery not only adds a new member to the Solar System’s family tree but also helps better understand the formation of KBOs.
“The discovery of satellites around all of the known large dwarf planets—except for Sedna—means that at the time these bodies formed billions of years ago, collisions must have been more frequent, and that’s a constraint on the formation models,” said Csaba Kiss of the Konkoly Observatory in Budapest, Hungary, lead author of the research. “If there were frequent collisions, then it was quite easy to form these satellites.”
Read the full article from NASA’s Goddard Space Flight Center here: Hubble Spots Moon Around Third Largest Dwarf Planet