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PIA15283: Dunes in Noachis Terra Region of Mars January 25, 2012

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http://photojournal.jpl.nasa.gov/jpegMod/PIA15283_modest.jpg
Description:

This enhanced-color image shows sand dunes trapped in an impact crater in Noachis Terra, Mars. Dunes and sand ripples of various shapes and sizes display the natural beauty created by physical processes. The area covered in the image is about six-tenths of a mile (1 kilometer) across.

Sand dunes are among the most widespread wind-formed features on Mars. Their distribution and shapes are affected by changes in wind direction and wind strength. Patterns of dune erosion and deposition provide insight into the sedimentary history of the surrounding terrain.

The image is one product from an observation by the High Resolution Imaging Science Experiment (HiRISE) camera taken on Nov. 29, 2011, at 42 degrees south latitude, 42 degrees east longitude. Other image products from the same observation are at http://www.uahirise.org/ESP_025042_1375.

HiRISE is one of six instruments on NASA’s Mars Reconnaissance Orbiter. The University of Arizona, Tucson, operates the orbiter’s HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Science Mission Directorate, Washington.

Image Credit:

NASA/JPL-Caltech/Univ. of Arizona

Image Addition Date:

2012-01-25

Evidence for Two More Earth-Sized Planets …Orbiting Former Red Giant Star January 11, 2012

Posted by jtintle in Deep Space, Space Fotos.
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Artist's rendition of two hot Earth-sized planets orbiting a subdwarf B star, KOI 55. (Illustration: S. Charpinet)

Explanation:

[Note: The “modulations in the pulsations” in the star’s brightness, referred to in the article, are not transit signals, and these are not confirmed planets by the criteria and established methods of the Kepler Science Team.]

Article excerpts: …two planets, KOI 55.01 and KOI 55.02, orbit the star KOI 55, a subdwarf B star, which is the leftover core of a red giant star. …According to lead author Stephane Charpinet, “Having migrated so close, they probably plunged deep into the star’s envelope during the red giant phase, but survived” …(albeit “deep-fried”). They are estimated to have radii of 0.76 and 0.87 that of Earth, the smallest … so far orbiting an active star. …the star had already been the subject of study using the telescopes at Kitt Peak National Observatory, part of a project to examine pulsating stars. …the team used data from the orbiting Kepler space telescope which is free of interfering atmospheric effects. …Two tiny modulations in the pulsations of the star were found, which further analysis indicated could only come from planets passing in front of the star (from our viewpoint) every 5.76 and 8.23 hours.

See the abstract of the paper on the Nature website. Downloading the full article requires a single-article payment of $32.00 US or a subscription to Nature.

See also University of Arizona press release of 2011 December 21, by Daniel Stolte, Excerpts from press release: …Two Earth-sized planets … circling a dying star that has passed the red giant stage. Because of their close orbits, the planets must have been engulfed by their star while it swelled up to many times its original size. …Researchers believed that this unimaginable inferno would make short work of any planet caught in it – until now. …The team was led by Stephane Charpinet, an astronomer at the Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse-CNRS, in France.

…The two planets, named KOI 55.01 and KOI 55.02, circle their host star in extremely tight orbits. Having migrated so close, they probably plunged deep into the star’s envelope during the red giant phase, but survived….

The host star, KOI 55, is what astronomers call a subdwarf B star: It consists of the exposed core of a red giant that has lost nearly its entire envelope. In fact, the authors write, the planets may have contributed to the increased mass loss necessary for the formation of this type of star.

The authors concluded that planetary systems may therefore influence the evolution of their parent stars.

…the research team had not set out to find new planets far away from our solar system, but to study pulsating stars. Caused by rhythmic expansions and contractions brought about by pressure and gravitational forces that go along with the thermonuclear fusion process inside the star, such pulsations are a defining feature of many stars.

By studying the pulsations of a star, astronomers can deduce the object’s mass, temperature, size and sometimes even its interior structure. This is called asteroseismology.

“Those pulsation frequency patterns are almost like a finger print of a star,” Green said. “It’s very much like seismology, where one uses earthquake data to learn about the inner composition of the Earth.” … the team used data obtained from NASA’s Kepler Space Telescope for this study.

…While analyzing KOI 55’s pulsations, the team noticed the intriguing presence of two tiny periodic modulations occurring every 5.76 and 8.23 hours that caused the star to flicker ever so slightly, at one five thousandth percent of its overall brightness. They showed that these two frequencies could not have been produced by the star’s own internal pulsations.

The only explanation came from the existence two small planets passing in front of the star every 5.76 and 8.23 hours. To complete their orbits so rapidly, KOI 55.01 and KOI 55.02 have to be extremely close to the star, much closer than Mercury is to our sun. On top of that, the sun is a cool star compared to KOI 55, which burns at about 28,000 Kelvin, or 50,000 degrees Fahrenheit.

…”We think this is the first documented case of planets influencing a star’s evolution,” Charpinet said. …”I find it incredibly fascinating that after hundreds of years of being able to only look at the outsides of stars, now we can finally investigate the interiors of a few stars – even if only in these special types of pulsators – and compare that with how we thought stars evolved,” Green said. “We thought we had a pretty good understanding of what solar systems were like as long as we only knew one – ours. Now we are discovering a huge variety of solar systems that are nothing like ours, including, for the first time, remnant planets around a stellar core like this one.”

Credits:

Illustration: S. Charpinet; sources: UANews and Universe Today,  Nature,  NASA,  Daniel Stolte, Kepler Space Telescope,  Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse-CNRS, Elizabeth ‘Betsy’ Green

The Crazy Floor of Hellas Basin July 30, 2011

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The Crazy Floor of Hellas Basin

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Explanation:

The deep floor of Hellas impact basin is often obscured by haze, but at times we get some clear views. There are some strange landforms down there, and this image is one example.

The image covers the rim region of a crater that appears filled in, perhaps by river sediment (the rim is breached by a channel). The colors (see enhanced color subimage) indicate that diverse minerals are present.

Written by:

Alfred McEwen   (27 July 2011)

A Dark Dune Field in Proctor Crater on Mars November 28, 2010

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See Explanation.  Clicking on the picture will download  the highest resolution version available.

Credit:

HiRISE, MRO, LPL (U. Arizona), NASA

Explanation:

Was this image taken with a telescope or a microscope? Perhaps this clue will help: if the dark forms were bacteria, they would each span over football field across. What is actually being seen are large sand dunes on the floor of Proctor Crater on Mars. The above picture was taken by HiRISE camera on board the Mars Reconnaissance Orbiter (MRO), a robot spacecraft currently in orbit around Mars. The dark rippled dunes likely formed more recently than the lighter rock forms they appear to cover, and are thought to slowly shift in response to pervasive winds. The dunes arise from a complex relationship between the sandy surface and high winds on Mars. Similar dunes were first seen in Proctor Crater by Mariner 9 more than 35 years ago.

Flame Nebula Close-Up November 28, 2010

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See Explanation.  Clicking on the picture will download  the highest resolution version available.

Image Credit & Copyright:

Adam Block, Mt. Lemmon SkyCenter, U. Arizona

Explanation:

Of course, the Flame Nebula is not on fire. Also known as NGC 2024, the nebula’s suggestive reddish color is due to the glow of hydrogen atoms at the edge of the giant Orion molecular cloud complex some 1,500 light-years away. The hydrogen atoms have been ionized, or stripped of their electrons, and glow as the atoms and electrons recombine. But what ionizes the hydrogen atoms? In this close-up view, the central dark lane of absorbing interstellar dust stands out in silhouette against the hydrogen glow and actually hides the true source of the Flame Nebula’s energy from optical telescopes. Behind the dark lane lies a cluster of hot, young stars, seen at infrared wavelengths through the obscuring dust. A young, massive star in that cluster is the likely source of energetic ultraviolet radiation that ionizes the hydrogen gas in the Flame Nebula.

Eroding Layers in an Impact Crater February 13, 2010

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Eroding Layers in an Impact Crater

Credit:

NASA/JPL/University of Arizona, Colin Dundas

Description:

This image shows a stack of layers on the floor of an impact crater roughly 30 kilometers across. Many of the layers appear to be extremely thin, and barely resolved.

In broad view, it is clear that the deposit is eroding into a series of ridges, likely due to the wind. Below the ridges, additional dark-toned layered deposits crop out. These exhibit a variety of textures, some of which may be due to transport of material.

The light ridges are often capped by thin dark layers, and similar layers are exposed on the flanks of the ridges. These layers are likely harder than the rest of the material, and so armor the surface against erosion. They are shedding boulders which roll down the slope, as shown in the subimage. Although these cap layers are relatively resistant, the boulders do not seem to accumulate at the base of the slope, so it is likely that they also disintegrate relatively quickly.

The subimage itself is 250 meters wide. The light is from the left. Boulders are visible on the slopes of the ridges along with thin dark layers including the cap layer, but they are absent on the spurs where the resistant cover has been eroded. This demonstrates that the boulders come only from the dark layers, and are not embedded in the rest of the deposit.

Alluvial Fans in Mojave Crater: Did It Rain on Mars? January 8, 2010

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Alluvial Fans in Mojave Crater: Did It Rain on Mars?

Credit:

NASA/JPL/University of Arizona, Alfred McEwen

Description:

Aptly-named Mojave Crater in the Xanthe Terra region has alluvial fans that look remarkably similar to landforms in the Mojave Desert of southeastern California and portions of Nevada and Arizona.

Alluvial fans are fan-shaped deposits of water-transported material (alluvium). They typically form at the base of hills or mountains where there is a marked break, or flattening of slope.

They typically deposit big rocks near their mouths (close to the mountains) and smaller rocks at greater distances. Alluvial fans form as a result of heavy desert downpours, typically thundershowers. Because deserts are poorly vegetated, heavy and short-lived downpours create a great deal of erosion and nearby deposition.

There are fans inside and around the outsides of Mojave crater on Mars that perfectly match the morphology of alluvial fans on Earth, with the exception of a few small impact craters dotting this Martian landscape.

Channels begin at the apex of topographic ridges, consistent with precipitation as the source of water, rather than groundwater. This remarkable landscape was first discovered from Mars Orbital Camera images. Mars researchers have suggested that impact-induced atmospheric precipitation may have created these unique landscapes.

This HiRISE image at up to 29 cm/pixel scale supports the alluvial fan interpretation, in particular by showing that the sizes of the largest rocks decrease away from the mouths of the fans.

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Dust and the Helix Nebula January 7, 2010

Posted by jtintle in Deep Space, Space Fotos.
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See Explanation.  Clicking on the picture will download  the highest resolution version available.
Credit:

NASA, JPL-Caltech, Kate Su (Steward Obs, U. Arizona) et al.

Explanation:

Dust makes this cosmic eye look red. The eerie Spitzer Space Telescope image shows infrared radiation from the well-studied Helix Nebula (NGC 7293) a mere 700 light-years away in the constellation Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula, representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula’s central star itself is immersed in a surprisingly bright infrared glow. Models suggest the glow is produced by a dust debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system’s Kuiper Belt or cometary Oort cloud. Formed in the distant planetary system, the comet-like bodies would have otherwise survived even the dramatic late stages of the star’s evolution.

The Trifid Nebula in Stars and Dust July 12, 2009

Posted by jtintle in Deep Space, Space Fotos.
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See Explanation.  Clicking on the picture will download the highest resolution version available.
Credit & Copyright:

Adam Block, Mt. Lemmon SkyCenter, U. Arizona

Explanation:

Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula. Also known as M20, this photogenic nebula is visible with good binoculars towards the constellation of Sagittarius. The energetic processes of star formation create not only the colors but the chaos. The red-glowing gas results from high-energy starlight striking interstellar hydrogen gas. The dark dust filaments that lace M20 were created in the atmospheres of cool giant stars and in the debris from supernovae explosions. Which bright young stars light up the blue reflection nebula is still being investigated. The light from M20 we see today left perhaps 3,000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20.

Starburst Spider (ESP_011842_0980) March 25, 2009

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Starburst Spider

Credit:

NASA/JPL/University of Arizona

Description:

Mars’ seasonal cap of carbon dioxide ice (dry ice) has eroded many beautiful terrains as it sublimates (goes directly from ice to vapor) every spring. In this region we see troughs that form a starburst pattern.

In other areas these radial troughs have been referred to as “spiders,” simply because of their shape. In this region the pattern looks more dendritic as channels branch out numerous times as they get further from the center. The troughs are believed to be formed by gas flowing beneath the seasonal ice to openings where the gas escapes, carrying along dust from the surface below. The dust falls to the surface of the ice in fan-shaped deposits.

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