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Trifid Nebula

Clouds of glowing gas mingle with dust lanes in the Trifid Nebula, a star forming region toward the constellation of the Archer (Sagittarius). In the center, the three prominent dust lanes that give the Trifid its name all come together. Mountains of opaque dust appear on the right, while other dark filaments of dust are visible threaded throughout the nebula. A single massive star visible near the center causes much of the Trifid’s glow.

The Trifid, also known as M20, is only about 300,000 years old, making it among the youngest emission nebulae known. The nebula lies about 9,000 light years away and the part pictured here spans about 10 light years.

Source: APOD

Stickney Crater - Phobos

Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet’s moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth’s gravity, streaks suggest loose material slid down inside the crater walls over time. Light bluish regions near the crater’s rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact.

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Gorgeous New NASA Photos Of Saturn’s Rings and Clouds

NASA has unveiled amazing new views of the planet Saturnshowcasing the ringed wonder’s moons, rings and turbulent atmosphere as seen by the Cassini spacecraft.

The first photo, which NASA released on Christmas Eve (Dec. 24), clearly shows Saturn’s south pole and distinctive rings. But the image also holds a few surprises.

The shadow of Saturn’s moon Mimas appears in the photo as a small, oblique dark spot slightly to the left and above the planet’s south pole. Mimas is perhaps best known for a huge crater that dominates one of its hemispheres, leading some “Star Wars” fans to compare its look to the “Death Star.”

Cassini also captured Janus, another of the more than 60 known moons of Saturn, in the top left section of the image. The small satellite is difficult to spot, but appears as a tiny white dot just over the planet’s north pole. While NASA released the photo of Saturn, Mimas and Janus this week, Cassini actually snapped the image in August. Since then, mission scientists processed and polished the image to highlight its features. 

A second Saturn photo, a raw, unprocessed view released Wednesday (Dec. 26), shows Saturn’s turbulent surface in extreme detail. Violent storms churning among Saturn’s cloud tops appear as delicate whorls and swirls.

Both of the new Saturn photos were taken with Cassini’s wide-angle camera, but they represent two different ways NASA handles space images. The first photo of Saturn, Janus and Mimas was refined to bring out the most interesting aspects of the photos. For example, Janus was barely visible in the original, raw image, so image specialists opted to brighten the small moon in the final, refined image.

The second image is part of a larger database of raw images that NASA releases online soon after they are sent to Earth by Cassini. Like the first photo, this somewhat foggy depiction of Saturn’s surface will eventually be treated to bring out its most stunning aspects.

The Cassini spacecraft has logged more than 3.8 billion miles (6.1 billion km) since its launch with the Huygens lander in 1997. Cassini arrived at Saturn in 2004 and dropped European-built Huygens onto the surface of Saturn’s moon Titan. The Cassini- Huygens mission is a joint project of NASA, the Italian Space Agency and the European Space Agency.

During its time in space, Cassini has taken more than 300,000 images of the Saturn and its moons. The spacecraft is currently in an extended phase of its mission that runs through 2017.

(Source: Yahoo!)

Curiosity Rover Prepares to Drill Into Rocks That May Have Once Been Wet

NASA’s Curiosity rover has explored a new area on Mars called Yellowknife Bay, which shows plenty of evidence of flowing water. The rover is preparing to drill into a rock nicknamed “John Klein” in the location in the next couple weeks, investigating its composition and searching for organics. This will be the first time that engineers have drilled into the surface of another planet.

Scientists already know that Curiosity’s explorations have taken it to a place that was basically an ancient riverbed. Now they are uncovering the complex geologic history of the area and have stumbled across many interesting features.

“The scientists have been let into the candy store,” said engineer Richard Cook, project manager for Curiosity, during a NASA teleconference on Jan. 15.

For the last few weeks, the rover has been moving from the plateau it landed on down a slope into a depression. As it descended, it passed through layers of rock that are increasingly older, taking it backwards into the planet’s history. Geologists are finding a lot of different rock types, indicating that many different geologic processes took place here over time.

Some of the minerals are sedimentary, suggesting that flowing water moved small grains around and deposited them, and other evidence suggests water moved through the rocks after they had formed. Tiny spherical concretions scattered through the rock were likely formed when water percolated through rock pores and minerals precipitated out. Other samples are cracked and filled with veins of material such as calcium sulfate, that were also formed when water percolated through the cracks and deposited the mineral.

“Basically these rocks were saturated with water,” said geologist John Grotzinger of Caltech, Curiosity’s project scientist, who added that these rocks indicate the most complex history of water that researchers have yet seen on Mars.

Curiosity brushed some of these rocks to remove their dust covering and then peered at them close-up with its high-resolution Mars Hand Lens Imager (MAHLI) camera. The rocks are sandstones containing larger grains up to 2 mm long surrounded by silt grains that are “finer than powdered sugar but coarser than sugar used to make icing,” said geologist R. Aileen Yingst of the Planetary Science Institute, a scientist on the MAHLI team.

Many of the grains are rounded, suggesting they were knocked about and worn down somehow. Because the grains are too large to have been carried by wind, they were most likely transported by water flowing at least 1 meter per second (2.2 mph). All these investigations suggest if you could go deep into Mars’ past and stand at the same spot as the rover, you’d probably see a river of flowing water with small underwater dunes along the riverbed.

The next step for Curiosity is to drill 5 centimeter holes into some of these rocks and veins to definitively determine their composition. Grotzinger said that the team will search for aqueous minerals, isotope ratios that could indicate the composition of Mars’ atmosphere in the past, and possibly organic material.

The drilling will probably take place within two weeks, though NASA engineers are still unsure of the exact date. The procedure will be “the most significant engineering thing we’ve done since landing,” said Cook, and will require several trial runs, equipment warm-ups, and drilling a couple test holes to make sure everything works. The team wants to take things as slowly as possible to correct for any problems that may arise, such as potential electrical shorts and excessive shaking of the rover.

Frozen Water and Organic Material Discovered on Mercury

For the first time, scientists have confirmed that the planet Mercury holds at least 100 billion tons of water ice as well as organic material in permanently shadowed craters at its north pole.

The findings come from NASA’s MESSENGER spacecraft, which has been in orbit around the solar system’s smallest and innermost planet since 2011. Researchers have suspected that ice could exist in such craters since 1992, when Earth-based radar measurements found bright areas at the planet’s polar regions. Craters in this area cast long shadows, which prevent any sunlight from reaching their floors.

Though alternative explanations had been put forward to account for the radar-bright areas, MESSENGER has provided convincing evidence for water ice on the planet closest to our sun, where surface temperatures can sometimes reach 800 degrees Fahrenheit. The results appeared in three studies Nov. 29 in Science.

MESSENGER was able to detect water ice because it carries a neutron spectrometer that looks at energetic neutrons bouncing off Mercury’s surface. Water gives off a characteristic neutron signature. The spacecraft measured the area around Mercury’s north pole and found this characteristic signature, suggesting that between 100 billion and 1 trillion tons of water ice was present somewhere in the area. But the neutron spectrometer has fairly low resolution, on the order of hundreds of miles, so it can’t definitively say if this water is inside the craters. (If it were outside, daytime temperatures would have boiled the water away.)

Image: The topographic height of craters and surface features at Mercury’s north pole (top) and a model of the maximum amount of sunlight received in this area (bottom). Neumann et al, Science, 10.1126/science.1229764

Because they contain no light, MESSENGER’s cameras can’t see right inside the permanently shadowed regions. But the spacecraft carries a useful workaround tool. To map its height above the surface, the probe uses an altimeter that shoots a 10-nanosecond infrared laser pulse at the ground and intercepts the returning beam.

“We can measure the energy that comes back from the laser,” said planetary scientist Gregory Neumann of NASA’s Goddard Spaceflight Center, and lead author on one of the Science studies. Though the number of photons coming back is slight, “we could expect to see glints of brightness from surface water ice.”

Early results from MESSENGER presented a puzzle. Not only were there no bright spots in the permanently shadowed craters where radar measurements suggested ice, the surface was actually much darker than Mercury’s average color. “We were really surprised by this,” said Neumann.

The spacecraft continued to search, examining more and more craters. Finally, the laser spotted some dazzling crater floors that were two to four times brighter than the rest of Mercury’s surface. This was finally good evidence for the long-sought water ice. By modeling the temperature in and around different craters, scientists were able to determine the northernmost craters stayed cold enough over millions of years to hold onto water ice.

But what about the strange dark craters? Radar measurements suggested ice, but MESSENGER wasn’t confirming the result. The temperature models showed that these craters corresponded exactly to regions that would sometimes receive a small amount of scattered sunlight. This itsy bit of energy would heat the frozen water’s surface enough to sublimate it away. Dark organic compounds dissolved in the ice got left behind as residue and would slowly form a black cover, about 8 to 11 inches thick, which protected any remaining ice from getting vaporized by random sunbeams.

The organic material is likely made of hydrocarbons like methane and ethane, commonly found in comets and asteroids. “At room temperature it would be kind of gooey stuff, to use the technical term,” said planetary scientist Sean Solomon of Columbia University, who leads the MESSENGER team. Because the layer is relatively thin, it’s invisible to radar.

The MESSENGER team now thinks they have a good story to explain how these polar cold traps work. Every once in a while, a comet or asteroid hits Mercury and gets annihilated. The vaporized material either floats out into space or gets blasted away by the sun but any that finds its way into a permanently shadowed region will settle down. Molecule by molecule, water and other compounds build up inside the craters. Those that never see a ray of sunlight contain mostly clean water ice. But if even a tiny amount of light intrudes, it may heat up the water and cause it to recede below a layer of organic material.

“These look like really good results, and I think they are very convincing,” said planetary scientist Johannes Benkhoff from the Institute of Planetary Research in Germany, who is the lead scientist on the European Space Agency’s BepiColombo mission, which is expected to orbit Mercury in 2022. MESSENGER will provide many follow-up opportunities for this later mission, which will have its own neutron spectrometer to map the water ice regions with greater resolution.

In addition to being an astounding result, the finding can help scientists better understand the history of Earth. Mercury is a terrestrial planet like our own and the ice provides evidence for geologically recent delivery of water and carbon-rich material to the inner solar system from comets and asteroids. This process very likely happened billions of years in the past, when the Earth first formed, creating our planet’s oceans and possibly seeding them with the material to produce life.

“There’s now this record on Mercury, a place where we least expected to find it, of this process,” said Solomon. “It gives us a window to understanding this delivery system.”