Yes, it’s true. As of today, August 15, NASA’s Cassini spacecraft has less than 31 days—one full month—left in operation and, sadly, its existence. On September 15, 2017, Cassini will end its mission with a controlled dive into Saturn’s atmosphere…a journey that it will not long survive. But up until the very end Cassini, which has been exploring the majestic ringed planet and its family of moons since it arrived in the summer of 2004, will be making scientific observations and sending the data back to us here on Earth—at least as long as it possibly can. That data, in fact, will still be en route across the 900 million miles of space between us and Saturn for almost an hour after the spacecraft will have succumbed to the forces of atmospheric entry.
When Cassini’s final signal is received on Earth it will be a ghost message, sent from a ship that no longer exists.
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
It’s August and one of the most highly-anticipated astronomical events of the 21st century is nearly upon us: the August 21 solar eclipse, which will be visible as a total eclipse literally across the entire United States…but that doesn’t mean everywhere in the United States. Totality will pass across the U.S. in a narrow band about 60 miles wide starting along the northern coast of Oregon at 10:18 a.m. local time (PDT) and ending along the coast of South Carolina at 2:48 p.m. EDT. But that’s just totality—the full eclipse event will actually begin much earlier than that and end later, and its visibility won’t be limited to only that path. And while it’ll be happening overhead in the daytime sky you’ll need the right equipment to view it safely, whether you’re in totality or not.
Wait, you say, what’s the difference between totality and…not totality? And how is it caused? And why is this a big deal at all? If you’re wondering those things (and perhaps others) then this post is just for you. Below are answers to some common—and certainly not dumb—questions about the solar eclipse, brought to you by yours truly (with a little help from NASA and other eclipse specialists.)
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.
It’s been known for a while (especially since the 2009 LCROSS impact experiment) that there is water on the Moon. But so far the largest volume has been found as ice inside the shadowed walls of craters on the Moon’s south pole, likely originating from ancient comet impacts. Now, using data collected by India’s Chandrayaan-1 lunar satellite, researchers from Brown University in Providence, Rhode Island have identified water inside ancient pyroclastic flows located across the Moon’s surface—water that must have come from inside the Moon itself.
“We observe the water in deposits that are at the surface today, but these deposits are the result of magma that originally comes from deep within the lunar interior,” said Ralph Milliken, a geologist at Brown and lead author of the study. “Therefore, because the products of the magma have water, the deep interior of the Moon must also contain water.”
While the age and origin of this indigenous interior water aren’t yet known, its availability near the surface would be a valuable asset for any future human settlements on the Moon.
Read the rest of this article by Samantha Mathewson on Space.com here: The Moon’s Interior Could Contain Lots of Water, Study Shows