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Polygonal Dunes on Mars

Polygons are of great interest because they often indicate the presence of shallow ice or of desiccation such as in a mud flat. However, nature sometimes seems too clever for us.

Polygons form by the intersecting ridges of sand dunes. If this deposit were to become indurated and eroded, we might not be able to tell that they originated as wind-blown dunes, and interpret the polygons as evidence for a dried-up lake, for example. Dunes often accumulate in the bottoms on craters, also a good setting for a (temporary) lake.

The illumination is coming from the upper left, so the bluish ridges are high-standing.

Long Day’s Journey into Night

Saturn’s shadow cuts sharply across its rings as the orbits of ring particles carry them suddenly from day to night. With no atmosphere to scatter light, shadows in space are much darker than we’re used to here on Earth.

The ghostly, transient features known as `spokes’ can be faintly seen in Saturn’s B ring. More on spokes can be found at ‘Tis the Season for Spokes and The Spoke Search.

This view looks toward the unilluminated side of the rings from about 47 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on March 5, 2013.

The view was obtained at a distance of approximately 891,000 miles (1.434 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 85 degrees. Image scale is 51 miles (82 kilometers) per pixel.

Baked Exoplanet Gets Lab Treatment

Don’t get too excited, an exoplanet hasn’t really been captured from the cosmic wilds. And no, one of NASA’s boffins isn’t really taking a pair of tongs to the upper atmosphere of a strangely tiny “hot-Jupiter” being baked by a Bunsen burner. The doctored photo is actually a fun metaphor for this golden age of exoplanetary science. In particularly, it illustrates what one NASA space telescope is doing to understand the chemistry and dynamics of a particular Jupiter-sized exoplanet located some 385 light-years away.

Of course, it would be preferential if we could directly sample an exoplanet’s atmosphere in a lab, but as all exoplanets orbit stars many light-years from the nearest Bunsen burner, astronomers need to think up novel techniques by which the atmospheres of exoplanets can be remotely probed. Enter the Spitzer Space Telescope, NASA’s premier infrared observatory, the inadvertent hero of exo-atmospheric science!

Launched in 2003, Spitzer was designed to observe the infrared universe — particularly star-forming molecular clouds and distant galaxies — but in 2005 it became famous for detecting infrared emissions from extra-solar planets, namely HD 209458b and TrES-1. Since then, Spitzer has continued to notch up some impressive exoplanetary discoveries.

“When Spitzer launched in 2003, we had no idea it would prove to be a giant in the field of exoplanet science,” said Michael Werner, Spitzer project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Now, we’re moving farther into the field of comparative planetary science, where we can look at these objects as a class, and not just as individuals.”

In a new study published in the Astrophysical Journal, astronomers have used Spitzer to watch an exoplanet complete a full orbit around its host star.

Over 6 days, the hot-Jupiter HAT-P-2b passed in front of its star, behind and back in front again. Interestingly, HAT-P-2b’s orbit is highly eccentric, meaning its orbital path takes it only 2.8 million miles from the star’s surface at closest approach and out to 9.3 million miles at its most distant. As a comparison, the solar system’s innermost planet, Mercury, orbits the sun every 88 days and doesn’t come closer than 28 million miles — HAT-P-2b is therefore a roasted planet, where rapid changes in its atmosphere can be expected from extreme heating.

Fortunately, because HAT-P-2b’s orbit is not only compact but also eccentric, astronomers have a wonderful opportunity to see these changes occur over a very short timescale.

Full Article Over at Discovery News

This image covers many shallow irregular pits with raised rims, concentrated along ridges and other topographic features. How did these odd features form?

One idea is that they could be from sublimation of shallow lenses of nearly pure ice, but why do the pits have raised rims? They can’t be impact craters with such fortuitous alignment and irregular margins. They aren’t wind-blown deposits because there are many boulders, too big to be moved by the wind. There are younger wind-blown drifts on top of the pits, and there’s no clear connection to volcanism.

Some speculate that there were ancient oceans over this region—could that somehow explain these features? Ancient glaciation is another possibility, perhaps depositing ice-rich debris next to topographic obstacles.Future images of this region may provide clues, but for now this is a mystery.

How Mars and Jupiter Formed from Space Rock Crashes

The violent space rock collisions that gave birth to Mars appear to be surprisingly different from those thought to form the rocky core of Jupiter, scientists say.

Image: An artist rendition of the interior of Mars. A new study suggests Mars formed from the collision of smaller space rocks than those that created the rocky core of Jupiter. Image added April 30, 2013. Credit: NASA/JPL-Caltech

The difference comes from variations in the disc of dust, ice and other particles that swirled around the sun in the early years of the solar system.

Researchers said there was a “gradient” in the size of planetesimals — an early stage of planet formation — that orbited the young sun. Planets that were further away from the sun were more likely to grow larger than worlds closer in, they added.

“This difference can be explained by the snow line,” said Hiroshi Kobayashi, a researcher at Nagoya University in Japan, referring to the zone in the solar system where it was cold enough for icy compounds to condense 4.5 billion years ago.

“If we consider terrestrial planets, this is close to the sun, this means the temperature was very high, and the main component of the solid was rock, or something like that,” Kobayashi added. “But if we consider the outer disc — in this case, the main component is ice — it probably was ice planetesimals [that formed Jupiter].”

Chondrites and Chondrules

Chondrites are stony meteorites. They’re the most common and probably the most fascinating type of meteorite. The meteor/meteorite that broke windows in the Russian city of Chelyabinsk this past February was a stony chondrite.

The composition of chondrites is very similar to the composition of the Sun, except that they’re lacking hydrogen and helium. So, if you’d like to hold a piece of the Sun in your palm, chondrites are about as close as you can get. Their name is derived from the chondrules (spherical inclusions) observed in most of them. Chondrules are only found in meteorites.

They’re over 4 billion years old — older than the Earth and other planets. Scientists previously identified meteorites by the crystals found within chondrules, but later they realized that chondrules may recrystallize during weathering processes once they reach the Earth’s surface. Sometimes a broken face of a meteorite is weathered in such a way that 3-D chondrules are seen (above at upper right corner). However, chrondules can be more easily studied by cutting the parent chrondite into slices. Shown at center is a a microscopic image of a 3 cm slice of a chondrite that was found in northwest Africa. — Mila Zinkova

Exoplanet Catalog Reveals 7 Possibly Habitable Worlds

A new catalog aims to list all the known planets in the galaxy that could potentially be habitable to life. The count is at seven so far, with many more to come, researchers said.

Image: More exoplanets than expected in the first year of the Habitable Exoplanets Catalog. Image released Dec. 6, 2012. Credit: PHL @ UPR Arecibo, ESA/Hubble, NASA

The online listing, called the Habitable Exoplanets Catalog, celebrated its first anniversary today (Dec. 5). When it was first released last year, it had two potential habitable planets to its name. According to lead researcher Abel Mendez, the team expected to add maybe one or two more in the catalog’s first year. The addition of five suspected new planets was wholly beyond anyone’s expectations.

“The main purpose is for research, but then I realized that also for the public, it was very important,” said Mendez, director of the University of Puerto Rico at Arecibo’s Planetary Habitability Laboratory.

Bright Clouds on Uranus

The false colors in this image indicate altitude.

Credit: Erich Karkoschka (University of Arizona) and NASA

The green and blue regions show where the atmosphere is clear, allowing sunlight to penetrate deep into Uranus. In the yellow and gray regions, a haze or cloud layer is reflecting sunlight away. Orange and red colors indicate very high clouds, like cirrus clouds on Earth.

Dwarf Planets of Our Solar System

— In 2006 the organization responsible for classifying celestial bodies, the International Astronomical Union, decided that a new class of objects was needed. The solar system’s erratic ninth planet, Pluto, was assigned to the new “dwarf planet” category along with four other bodies, all tinier than Earth’s moon. Some astronomers expect there may be as many as 50 dwarf planets in the solar system.

— Eris, the largest dwarf planet, is only slightly bigger than Pluto, at 1,445 miles in diameter (2,326 km). Discovered in 2003, Eris orbits at an average distance of 68 AU (that is, 68 times the Earth’s distance from the sun) and takes 561.4 Earth years to circle the sun. Eris has the orbit that is most highly inclined of all the dwarf planets, tilted nearly 47 degrees from the plane of the planets’ orbits. A day on Eris takes 25.9 hours. Eris has one moon, Dysnomia.

— Pluto, discovered in 1930, orbits the sun at an average of 39.5 times the Earth’s distance. Its diameter is 1,430 miles (2,302 km). Pluto takes 247.9 Earth years to orbit the sun, and its day is 6.39 times as long as Earth’s. Pluto has five known moons: Charon, Nix, Hydra and two that were recently discovered and have not yet been named.

— Haumea was discovered in 2003. This dwarf planet has an extremely elongated shape, with its longest dimension being about 1,218 miles long (1,960 km). Haumea rotates very rapidly and has the shortest day of all the dwarf planets, only 3.9 hours. Orbiting 43.1 times farther from the sun than Earth does, Haumea takes nearly 282 Earth years to complete one orbit. Haumea has two moons, Hi’iaka and Namaka.

— Makemake, discovered in 2005, has no known moons. Makemake orbits at 45.3 times Earth’s distance and takes more than 305 years to complete a circuit of the sun. Its day is 22.5 hours. Makemake’s average diameter is 882 miles (1,420 km).

— Ceres, first spotted by astronomers in 1801, was first called a planet and later an asteroid. In 2006 it was reclassified as a dwarf planet. Ceres is the closest dwarf planet to Earth, orbiting at only 2.8 times Earth’s distance from the sun. Its year takes 4.6 Earth years and its day is 9.1 hours. Ceres has no known moons.

Meet the Dwarf Planets of the Solar System (Countdown)

Images: Dwarf Planet Eris, Pluto’s Cosmic Twin

Planets.. Planets Everywhere

This artists’s cartoon view gives an impression of how common planets are around the stars in the Milky Way.

The planets, their orbits and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one.

NASA’s Prolific Planet-Hunting Mission Goes Into Overtime

NASA’s planet-hunting Kepler Space Telescope has begun its extended mission, which should keep the prolific instrument searching for alien worlds for another four years, agency officials announced today (Nov. 14).

Kepler officially embarked upon the extended mission after completing its 3 1/2-year prime mission, which aimed to determine how common Earth-like planets are throughout the galaxy. The extended phase, which NASA announced this past April, funds the instrument through at least fiscal year 2016.

Kepler is staring at more than 150,000 stars continuously. It detects exoplanets by noticing the tiny brightness dips caused when they transit — or cross the face of — these stars from the telescope’s perspective.

Artist’s Concept of Kepler-20e

NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet’s surface, but they are the smallest exoplanets ever confirmed around a star like our sun.

Kepler-20e is the first planet smaller than the Earth discovered to orbit a star other than the sun. A year on Kepler-20e only lasts 6 days, as it is much closer to its host star than the Earth is to the sun. The temperature at the surface of the planet, around 1400 degrees Fahrenheit, is much too hot to support life, as we know it.

Kepler-20e is likely to be entirely rocky and without an atmosphere. The planet is tidally locked, always showing the same side to its host star, as the moon to the Earth, and could have large temperature differences between its permanent night and day sides.

Alien Planets With Extra Suns Can Have Strange Orbits

The more stars a system of alien worlds starts with, the more likely those planets will orbit those stars at odd tilts, scientists say.

Image: An artist’s illustration of the alien solar system Kepler-47, a twin star system that is home to two planets. The planets have two suns like the fictional planet Tatooine in the “Star Wars” universe. Credit: NASA/JPL-Caltech/T. Pyle

The discovery, based on a study unveiled today (Nov. 14), suggests that even Earth’s own sun may have had a companion star early in its development.

In recent years, astronomers have detected hundreds of exoplanets — worlds circling distant stars. Many of these are “hot Jupiters” — gas giants like Jupiter or Saturn that are closer to their stars than Mercury is to the sun.

Researchers had thought hot Jupiters arose when giant planets were dragged inward by protoplanetary disks of gas and dust falling toward stars. However, this idea was recently cast into doubt by the surprising discovery that a major fraction of hot Jupiters have orbits that are tilted in respect to their stars’ rotation.

Stars all spin, just as Earth’s does, and their worlds often line up with this spin — they orbit around the equators of their stars and revolve in the same direction. However, sometimes alien planets have misaligned orbits instead, ones that are at slight or even sharp angles around their stars. The orbits of some exoplanets are so far tilted that they are actually backwards — they move in retrogradeorbits in exactly the opposite direction of their stars’ spin.

Scientists had thought if hot Jupiters were dragged toward their stars by protoplanetary disks, they would all end up in relatively normal orbits around the equators of their stars. However, astronomers recently discovered that a whopping 25 to 50 percent of these planets actually may have misaligned orbits.

“The misalignments seemed to point towards a much more volatile, violent evolutionary path for hot Jupiters,” said study author Konstantin Batygin, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.