Death of Triton
Like Phobos at Mars, Triton’s low orbit around its parent planet will result in its destruction some 3.6 billion years in the future. How exactly it will meet its end is still a matter of debate. Some speculate that the moon will succumb to increasing gravitational stress, leaving a path of debris along its orbit as it disintegrates to form a new - albeit temporary- ring formation around Neptune.
A day on Neptune is just 16 hours long, study reveals
A day on Neptune lasts precisely 15 hours, 57 minutes and 59 seconds, according to the first accurate measurement of its rotational period made by University of Arizona planetary scientist Erich Karkoschka.
Karkoschka examined more than 500 images of Neptune that were taken by the Hubble Space Telescope. Two cloud formations, similar to Jupiter’s famous Red Spot, stood out — the South Polar Feature and the South Polar Wave. After studying the Hubble images, taken over a span of 20 years, Karkoschka determined that these distinct features appeared precisely on schedule.
Examining a series of more detailed images taken in 1989 by NASA’s Voyager spacecraft, Karkoschka found six additional features on Neptune that rotated with regularity. This method will help astronomers understand more than just how often the sun rises and sets on the Neptune.
Refined measurements of the blue giant’s rotation will help astronomers gain a better understanding of how its mass is distributed. A faster rotation implies that more of the mass is closer to the center than previously thought, which could change existing models of the exterior planets.
Stunning new snaps of Neptune and Triton
Here are a couple of views of Neptune as you have probably never seen the planet before. They were captured earlier today by astronomer Mike Brown using a 10-meter (33 ft) telescope at the W. M. Keck observatory on Hawaii.
The icy world dazzles in orange with some bright features in this infrared view, where the bright places are high clouds where the sunlight reflects off of them before it had a chance to pass through much of the atmosphere. Dark is clear atmosphere full of methane absorbing most of the photons. The second image is a wide-angle view and includes the largest moon Triton. If you compare the two images of Neptune you can see that the planet has clearly rotated between them. It turns once on its axis in a little over 16 hours.
Voyager 2 acquired the images for this high-resolution mosaic of Triton on August 25, 1989. The south pole is at the right; several of Triton’s famous south polar geysers are visible. Toward the equator at right, Triton is covered with a strange “cantaloupe terrain”.
A relatively new version of Voyager 2’s highest-resolution mosaic on Triton put together by Paul Schenk shows lots of tiny little craters on Triton’s cryovolcanic plains, most of them less than 20 kilometers in diameter.
Paul, with coauthor Kevin Zahnle, published a paper in 2007 in which they proposed that the 100 or so impact craters visible in the mosaic are “sesquinaries,” resulting from an impact onto or disruption of one of Neptune’s other moons, an event that would have created a population of shrapnel in Neptune orbit that could have produced all (or, at least, most) of Triton’s craters in one event. If this explanation were true, the craters could have formed as recently as yesterday (geologically speaking).
• Source: The Planetary Society Blog • View High-Res Image: 2500×2500 px
Cometary Impact on Neptune
A comet may have hit the planet Neptune about two centuries ago. This is indicated by the distribution of carbon monoxide in the atmosphere of the gas giant. Scientists analyzed data taken by Herschel space observatory, that has been orbiting the Sun in a distance of approximately 1.5 million km since May 2009.
In February 2010 scientists from Max Planck Institute discovered strong evidence for a cometary impact on Saturn about 230 years ago. Now new measurements performed by the instrument PACS on board the Herschel indicate that Neptune experienced a similar event.
Neptune’s atmosphere mainly consists of hydrogen and helium with traces of water, carbon dioxide and carbon monoxide. Now, the scientists detected an unusual distribution of carbon monoxide in the upper layer of the atmosphere, the socalled stratosphere. The only explanation for these results is a cometary impact.
Such a collision forces the comet to fall apart while the carbon monoxide trapped in the comet’s ice is released and over the years distributed throughout the stratosphere. From this distribution scientists can therefore derive the approximate time when the impact took place, confirming the earlier assumption that a comet hit Neptune two hundred years ago.
In Neptune’s stratosphere the scientists also found a higher concentration of methane. On Neptune, methane plays the same role as water vapor on Earth: the temperature of the socalled tropopause - a barrier of colder air separating troposphere and stratosphere - determines how much water vapor can rise into the stratosphere. If this barrier is a little bit warmer, more gas can pass through. On Neptune the tropopause’s mean temperature is -219°C.
Therefore, a gap in the barrier of the tropopause seems to be responsible for the elevated concentration of methane on Neptune. With minus -213°C, at Neptune’s southern Pole this air layer is six degrees warmer than everywhere else allowing gas to pass more easily from troposphere to stratosphere.
Source: Max Planck Institute for Solar System Research.
Taken in 1989 by Voyager 2 during its flyby of the Neptune system, this is a global color mosaic of Triton. With a radius about 22% smaller than Earth’s moon, Triton is the largest satellite of Neptune and is one of the few bodies in the solar system known to have a nitrogen-dominated atmosphere. The others are Earth and Saturn’s giant moon, Titan.
Triton is so cold that most of its nitrogen is condensed as frost, making it the only satellite in the solar system known to have a surface made mainly of nitrogen ice. The pinkish deposits constitute a vast south polar cap believed to contain methane ice. The dark streaks overlying these pink ices are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby.
The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of “cryovolcanic” landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton’s interior.
Image: 4500 × 3500 px (1.96 MB, JPG) | Image Credit: NASA/JPL/USGS
Triton’s Summer Sky of Methane and Carbon Monoxide
Astronomers have found real evidence that the Sun still makes its presence felt on Triton, even from so far away. This icy moon actually has seasons just as we do on Earth, but they change far more slowly.
According to the first ever infrared analysis of the atmosphere of Neptune’s moon Triton, summer is in full swing in its southern hemisphere. Now, using the CRIRES instrument at ESO’s Very Large Telescope, astronomers have made the first ground-based detection of carbon monoxide and methane in Triton’s thin atmosphere, revealing that the thin atmosphere varies seasonally, thickening when warmed.
On Triton, where the average surface temperature is about minus 235 degrees Celsius, it is currently summer in the southern hemisphere and winter in the northern. As Triton’s southern hemisphere warms up, a thin layer of frozen nitrogen, methane, and carbon monoxide on Triton’s surface sublimates into gas, thickening the icy atmosphere as the season progresses during Neptune’s 165-year orbit around the Sun. A season on Triton lasts a little over 40 years, and Triton passed the southern summer solstice in 2000.
Of Neptune’s 13 moons, Triton is by far the largest, and, at 2700 kilometres in diameter (or three quarters the Earth’s Moon), is the seventh largest moon in the whole Solar System. Since its discovery in 1846, Triton has fascinated astronomers thanks to its geologic activity, the many different types of surface ices, such as frozen nitrogen as well as water and dry ice (frozen carbon dioxide), and its unique retrograde motion.
Image: Artist’s impression of how Triton, Neptune’s largest moon, might look from high above its surface. The distant Sun appears at the upper-left and the blue crescent of Neptune right of centre.
Uranus & Neptune Have Seas of Diamond—With Diamond Icebergs
Both Uranus and Neptune have quirky magnetic poles—they’re located about 60 degrees off the geographic pole rather than very nearby, like ours is. The reason, researchers suggest in a new Nature Physics study, could be that oceans of diamond cover our solar system’s two most distant planets.
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New Evidence For Seas of Liquid Diamond On Neptune
Remote gas giant planets Neptune and Uranus could be covered in vast seas of liquid diamond, dotted with solid diamond chunks like icebergs. A new experiment revealed such oceans are plausible, and would explain some oddities about Neptune’s magnetic field.
Published recently in Nature Physics, the study is an effort to explain two things: What causes the magnetic poles of Neptune and Uranus to be so far off their geographic poles; and what would cause the planets to have a 10 percent carbon makeup. Diamond seas are the answer, and their experiment suggested that these seas would behave a lot like water oceans.
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