The colorful globe of Saturn’s largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA’s Cassini spacecraft. The north polar hood can be seen on Titan (5,150 km across or 3,200 mi) and appears as a detached layer at the top of the moon here. This view looks toward the northern, sunlit side of the rings from just above the ring plane.
Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft narrow-angle camera on 21 May 2011, at a distance of approximately 2.3 million km (1.4 million mi) from Titan. Image scale is 14 km (9 mi) per pixel on Titan.
This was obtained during the tenth orbit of Jupiter by NASA’s Galileo spacecraft. Io, which is slightly larger than Earth’s moon, is the most volcanically active body in the solar system. In this enhanced color composite, deposits of sulfur dioxide frost appear in white and grey hues while yellowish and brownish hues are probably due to other sulfurous materials.
Bright red materials, such as the prominent ring surrounding Pele, and “black” spots with low brightness mark areas of recent volcanic activity and are usually associated with high temperatures and surface changes. One of the most dramatic changes is the appearance of a new dark spot (upper right edge of Pele), 400 kilometers (250 mi) in diameter which surrounds a volcanic center named Pillan Patera. The dark spot did not exist in images obtained 5 months earlier, but Galileo imaged a 120 km (75 mi) high plume erupting from this location during its ninth orbit.
North is to the top of the picture which was taken on September 19, 1997 at a range of more than 500,000 kilometers (310,000 miles) by the Solid State Imaging (SSI) system on NASA’s Galileo spacecraft.
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA’s Office of Space Science, Washington, DC.
This five-frame sequence of New Horizons images captures the giant plume from Io’s Tvashtar volcano. Snapped by the probe’s Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Jupiter earlier this year, this first-ever “movie” of an Io plume clearly shows motion in the cloud of volcanic debris, which extends 330 kilometers (200 mi) above the moon’s surface. Only the upper part of the plume is visible from this vantage point — the plume’s source is 130 kilometers (80 mi) below the edge of Io’s disk, on the far side of the moon…
License to Chill (or, the solar system’s icy moons)
by Emily Lakdawalla
A week ago yesterday, at the Lunar and Planetary Science Conference, I faced a choice between attending the third full session on Curiosity results or a session that covered at least eight entire worlds (including Ganymede, Europa, Dione, Rhea, Mimas, Tethys, Enceladus, and Miranda).
If I may editorialize a bit: I do think it’s appropriate at a science meeting to give new missions a somewhat disproportionate share of oral session time. With new data coming in from new kinds of instruments from new locations there is high potential for surprising results, observations that falsify or confirm the hypotheses that sent a spacecraft to a new place.
However, I do think that three full oral sessions devoted to Curiosity results was excessive, especially given how much Curiosity was discussed in all the other cross-disciplinary Mars sessions over the course of the rest of the week. So, on Tuesday morning, I attended the icy moons session (amusingly titled “License to Chill”) and enjoyed its variety!
By way of introduction, here are those eight worlds I mentioned. Ganymede, on the left, is the largest moon in the solar system, larger than Mercury. Next to it is Europa, the smallest of Jupiter’s four Galilean satellites. Next to that is Miranda, the smallest of Uranus’ major icy moons and the only one that Voyager 2 got great photos of…
The three snapshots of the volcanic moon rounding Jupiter were taken over a 1.8-hour time span. Io is roughly the size of Earth’s moon but 2,000 times farther away. In two of the images, Io appears to be skimming Jupiter’s cloud tops, but it’s actually 310, 000 miles (500,000 kilometers) away. Io zips around Jupiter in 1.8 days, whereas the moon circles Earth every 28 days.
The conspicuous black spot on Jupiter is Io’s shadow and is about the size of the moon itself (2,262 miles or 3,640 kilometers across). This shadow sails across the face of Jupiter at 38,000 mph (17 kilometers per second). The smallest details visible on Io and Jupiter measure 93 miles (150 kilometers) across, or about the size of Connecticut.
A fluorescent glow high in the atmosphere of Titan, Saturn’s largest moon, signifies the presence of a gas that astronomers have yet to identify.
Data gathered by the Saturn-orbiting Cassini craft during Titan flybys show that the spectral emission is strongest at an infrared wavelength of about 3.28 micrometers. That wavelength is very near one where emissions of methane, a gas prevalent in Titan’s atmosphere, are also strong—one reason that emissions from the unknown gas were previously obscured, the researchers note.
A Window Into the Sub Ice Ocean of Jupiter’s Moon, Europa
If you could lick the surface of Jupiter’s icy moon Europa, you would actually be sampling a bit of the ocean beneath. A new paper by Mike Brown, an astronomer at the California Institute of Technology in Pasadena, Calif., and Kevin Hand from NASA’s Jet Propulsion Laboratory, also in Pasadena, details the strongest evidence yet that salty water from the vast liquid ocean beneath Europa’s frozen exterior actually makes its way to the surface.
The finding, based on some of the best data of its kind since NASA’s Galileo mission (1989 to 2003) to study Jupiter and its moons, suggests there is a chemical exchange between the ocean and surface, making the ocean a richer chemical environment. The work is described in a paper that has been accepted for publication in the Astronomical Journal.
The exchange between the ocean and the surface, Brown said, “means that energy might be going into the ocean, which is important in terms of the possibilities for life there. It also means that if you’d like to know what’s in the ocean, you can just go to the surface and scrape some off.” …
Images taken by the Hubble Space Telescope in 2011 and 2012 revealed two previously unknown moons of Pluto. So far, we have been calling them “P4” and “P5”, but the time has come to give them permanent names. If it were up to you, what would you choose?
By tradition, the names of Pluto’s moons come from Greek and Roman mythology, and are related to the ancient tales about Hades and the Underworld. Please pick your favorites on the ballot below.
Alternatively, if you have a great idea for a name that we have overlooked, let us know by filling out the write-in form. If you can make a good case for it, we will add it to the list. See the blog page for the latest info.
Ground Rules: Feel free to come back, but please do not vote more than once per day, just so everybody gets a fair chance to make their opinion known. We will take your votes and suggestions into consideration when we propose the names for P4 and P5 to the International Astronomical Union (IAU). Voting ends at noon EST on Monday, February 25th, 2013.
via: Mark Showalter, for the P4/P5 Discovery Team
Carl Sagan Center for the Study of Life in the Universe, SETI Institute
As part of the first demonstration of laser communication with a satellite at the moon, scientists with NASA’s Lunar Reconnaissance Orbiter (LRO) beamed an image of the Mona Lisa to the spacecraft from Earth.
The iconic image traveled nearly 240,000 miles in digital form from the Next Generation Satellite Laser Ranging (NGSLR) Station at NASA’s Goddard Space Flight Center in Greenbelt, MD, to the Lunar Orbiter Laser Altimeter (LOLA) instrument on the spacecraft. By transmitting the image piggyback on laser pulses that are routinely sent to track LOLA’s position, the team achieved simultaneous laser communication and tracking.
As the long winter night deepens at Jupiter’s moon, Enceladus’ south pole, its jets are also progressively falling into darkness. The shadow of the moon itself is slowly creeping up the jets making the portions closest to the surface difficult to observe by the Cassini spacecraft. Cassini looks toward the night side of Enceladus (313 mi, or 504 km across) in this image. Enceladus is lit by light reflected off Saturn rather than by direct sunlight.
This view looks toward the Saturn-facing hemisphere of Enceladus. North on Enceladus is up. The image was taken with the Cassini spacecraft narrow-angle camera on Sept. 24, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 930 nanometers. The view was acquired at a distance of approximately 452,000 miles (728,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 170 degrees. Scale in the original image was 3 miles (4 kilometers) per pixel. The image was magnified by a factor of three to enhance the visibility of jets.
The leading hypothesis for the origin of the Moon involves a huge collision between the Earth and a planet half its size. That concept is often called the Giant Impact Hypothesis. This hypothesis suggests some of the colliding material was added to the Earth, while a large fraction of the impact debris went into orbit around the Earth. The orbiting material then accreted together to form the Moon. The collision and subsequent accretion of the Moon occurred 4.5 billion years ago.
Another day, another study identifying more potentially habitable worlds in the Kepler data, this time by professional astronomers and volunteers called the Planet Hunters who discussed their planet detections on a specialized message board system called Talk.
What they found was that more gas giants orbited stars in their habitable zones than initially thought, giving real evidence for the hypothesis that while alien Earths could be somewhat rare, moons orbiting alien Jupiters and Saturns may be a fairly common habitat for extraterrestrial life. Trouble is that we can’t see these moons or detect the wobble of the planets they orbit, so we don’t know how many of them there are, how big they are on average, and their likely composition. However, we do have very good reasons to assume that they could be there since gas giants in our own solar system are swarmed by moons of all shapes and sizes, and some are very possible hosts to life…
GENESIS II: EXTRATERRESTRIAL OCEANS COULD HOST LIFE
by Ray Villard
NASA’s battle cry behind the small armada of orbiters, landers and rovers dispatched to Mars is “follow the water!” Where there’s water, there could be life, which needs a solvent like water to assemble the complex macromolecules needed for living systems.
Mars is covered with geological evidence that it was once a soggy planet. But no longer. One of the most exciting findings to date from the roving field geologist, the Mars Science Laboratory Curiosity, was the detection of a dried up ancient stream where water once flowed billions of years ago.
The irony is that if you travel a couple hundred million miles beyond Mars’ orbit you cross the solar system’s frost line, the boundary beyond which there is plenty of water preserved from the planets’ birth.
At least six outer moons have subsurface oceans that could potentially be cozy places for life: Europa, Ganymede, Callisto, Titan, Enceladus and Triton. Each of them could have as much if not more water than found in all of Earth’s oceans. In fact Earth is a comparatively dry world.
The idea of a stellar habitable zone, where water can remain stable on a planet’s surface, was scientifically spelled out and popularized by Michael Hart in the late 1970s. Since such a zone is a narrow slice of the solar system’s real estate, Hart used his widely cited research paper to support the Rare Earth hypothesis:that the evolution of complex life would be hard to replicate in the cosmos.
Today, the concept of a habitable zone is old fashioned says Ken Hand of NASA’s Jet Propulsion Laboratory. “The Goldilocks scenario is outdated. There are new ways to mediate habitability via tidal interactions.”...