Behold the first geological map of Ganymede, Jupiter’s largest moon
by Lauren Davis
Four hundred years ago, Galileo Galilei observed Ganymede in orbit around Jupiter. This week, a team of planetary scientists unveiled the first global geological map of our solar system’s largest moon.
Using images obtained by NASA’s Voyager 1 and 2 spacecraft and the Galileo orbiter, a team led by Geoffrey Collins of Wheaton College pieced together a mosaic image of the planet, giving us our first complete image of the geological features of the satellite. Above, you can see the moon centered at 200 west longitude. The darker areas represent the very old and heavily cratered region of Ganymede, while the lighter areas are somewhat younger regions marked with grooves and ridges…
Europa New Frontiers Mission? (Or why I like the Europa Clipper concept even more now)
by Van Kane
Jupiter’s moon Europa has been a priority destination for NASA’s planetary program since the mid-1990s. With a deep ocean trapped beneath an icy shell on top and the rocky surface below, Europa is believed to have the chemicals and energy needed to host life. Over the course of almost two decades, I’ve seen plans for a better, really cheaper, faster mission that just needed a lot of new technology to be developed.
As if to balance that plan out, there was a plan for the planetary equivalent of a Battlestar Galactica mission that was both unaffordable and also required technology that still doesn’t exist. I thought we were close with the Jupiter Europa Orbiter (JEO, circa 2010) until new cost estimates showed that it, too, was unaffordable.
Now we have a proposed mission, the Europa Clipper, that doesn’t require substantial technology development and that has a cost estimate (~$2B) that puts it well within the cost range of NASA’s larger science missions. However, in today’s era of declining US federal budgets, the Clipper’s price tag is deemed unaffordable.
In a conversation with scientists on a NASA advisory panel, the head of the space agency’s Science program, John Grunsfeld discussed whether NASA should look at a Europa mission for half that of the Clipper mission. If it could be done, then a Europa mission could fit in the established New Frontiers program of planetary missions. (I want to emphasize that Grunsfeld’s conversation was informal and wasn’t announcing a policy decision.)…
Icy Europa May Be First Alien World Found With Active Plate Tectonics
by Betsy Mason
Scientists may have spotted the first evidence for active plate tectonics on another world. Jupiter’s moon Europa is covered in an ice crust bearing scars that may reveal movement similar to that of Earth’s rocky plates.
Europa was already considered to be among the most scientifically intriguing bodies in the solar system and one of the most promising places to hunt for life in the solar system because of the liquid ocean that resides beneath its crust. If the latest findings turn out to be true, it could be another point in favor of the moon’s potential habitability by providing a way to get nutrients from the surface down into the ocean.
“What’s exciting is that this would be the only other place outside of Earth where a plate-tectonic-style system is occurring,” said planetary scientist Alyssa Rhoden, a NASA postdoctoral program fellow who studies Europa, but was not involved in the new research…
Near-infrared color composite image of Saturn’s largest moon Titan taken with the Keck II adaptive optics system. Titan’s surface appears red, while haze layers at progressively higher altitudes in the atmosphere appear green and blue.
Image Credit: W. M. Keck Observatory/SRI/New Mexico State University
An icy moon of Jupiter has been caught spitting into space. For the first time, a towering plume of water vapour has been seen coming from Europa. The discovery strengthens the case that the moon has a liquid ocean beneath its icy crust, and may even offer a way to taste its seas and search for signs of life…
A quintet of Saturn’s moons dance elegantly above the planet’s famed rings in this photo taken by the Cassini spacecraft and released November 4.In orbit around the ringed planet since 2004, Cassini has offered unparalleled views of Saturn’s rings and moons, including this picture shot from slightly above the plane of the rings.
On the right, the closest moon is Rhea, which is Saturn’s second-largest satellite, and in the center is Enceladus, shining brightly with frost vented from its south pole geysers.
(Phys.org) —With the sun now shining down over the north pole of Saturn’s moon Titan, a little luck with the weather, and trajectories that put the spacecraft into optimal viewing positions, NASA’s Cassini spacecraft has obtained new pictures of the liquid methane and ethane seas and lakes that reside near Titan’s north pole. The images reveal new clues about how the lakes formed and about Titan’s Earth-like “hydrologic” cycle, which involves hydrocarbons rather than water… (read more)
Image: NASA/JPL-Caltech/University of Arizona/Univ. of Idaho
Carlson reported that new methods for dating rocks from the Moon’s crust or regolith have placed its birth between 4.4 and 4.45 billion years ago. Previously, scientists placed its origin at 4.56 billion years ago. The Moon was formed when a Mars-sized body smashed into the Earth, reducing part of our planet to liquid rock and shooting debris into orbit that slowly cooled and coalesced into the Moon…
Gemini North infrared image of Saturn and Titan (at about 6 o’clock position). Image obtained on May 7, 2009 (5:31 UTC), using the Altair adaptive optics system with the Near-infrared imager (NIRI). Color composite image made using data from three infrared filters (K’ [2.0-2.1 microns], h210 [2.12 mircon narrowband], and bracket gamma [2.17 micron narrowband]), field of view is about 40 arcseconds across.
At the edges of Saturn’s ring, the F-ring is faintly visible. The F-ring was discovered in images from the Pioneer 11 spacecraft in 1979 and is normally not apparent in images taken with ground-based telescopes. Also apparent are several of Saturn’s smaller moons.
Image: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai’i [high-resolution]
A true-color image of Io, one of the moons of Jupiter, taken by the Galileo spacecraft. The dark spot just left of center is the erupting volcano Prometheus. Whitish plains on either side of it are coated with volcanically emplaced sulfur dioxide frost, while yellower regions are encrusted with a higher proportion of sulfur.
… is the larger and closer of the two natural satellites of Mars. With a mean radius of 11.1 km (6.9 mi), Phobos is 7.24 times as massive as the second moon Deimos. It is named after the Greek god Phobos (which means “fear”), a son of Ares (Mars) and Aphrodite (Venus) . Both moons were discovered in 1877.
A small, irregularly shaped object, Phobos orbits about 9,400 km (5,800 mi) from the center of Mars, or about 6,000 km (3,700 mi) from the Martian surface, closer to its primary than any other known planetary moon. Phobos is one of the least reflective bodies in the Solar System, and features a large impact crater, Stickney. It orbits so close to the planet that it moves around Mars faster than Mars rotates. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 h 15 min or less, and set in the east twice each Martian day. Due to its short orbital period and tidal interactions, Phobos’s orbital radius is decreasing and it will eventually break up into a planetary ring…
The rings of Uranus are shown here captured almost exactly edge-on to Earth. This false-colour image was obtained by the NAOS-CONICA infrared camera on ESO’s Very Large Telescope at Paranal, Chile. It was taken at 9:00 UT on 16 August 2007, just two hours after Earth had crossed to the lit side of the ring plane.
We are peering over the sunlit face of the rings at an opening of only 0.003 degree, an angle so small that the thin rings nearly disappear. At right, the region around the planet has been enhanced to show a thin line, which is sunlight glinting off the ring edges and also reflected by dust clouds embedded within the system. The pictures at left shows the planet and identifies four of its largest moons. One can clearly discern banding in the atmosphere and a bright cloud feature near the planet’s south polar collar, on the left side of the image. This is a composite of images taken at infrared wavelengths…
The Moon’s Mystery: Scientists Debate How it Formed
How was our planet’s satellite formed? Scientists are still searching for the answer.
by Robert Irion
It has taken centuries for scientists to settle on a creation story for our moon, the most popular of which is depicted on the July cover of National Geographic magazine. But as I learned at a recent lunch with Erik Asphaug, a planetary scientist at Arizona State University, the debate is still far from finished.
Before the giant impact model gained traction nearly four decades ago, three other models were in contention. One said the moon condensed from the same whirling cloud of dust that created Earth. But this “binary” model couldn’t explain why the moon, far from being a smaller twin of Earth, is much less dense than our planet, with no iron core.
A second model held that the young molten Earth spun so rapidly that it split apart, flinging a giant blob of magma into space. But Earth’s spin today and the moon’s orbit don’t fit the pattern predicted by the “fission” model.
In the third model, Earth’s gravity lassoed the moon as it wandered through from some distant part of the solar system. This “capture” scenario was appealing until the Apollo astronauts brought their moon rocks back home. The minerals in them turned out to be similar to those in Earth’s mantle—not exotic at all.
The giant impact model avoided all these problems. When it came along in the 1970s, the model fit an emerging view of how the solar system as a whole had formed…