Caption Spotlight (16 May 2019): The Changing Surface of…

Caption Spotlight (16 May 2019): The Changing Surface of Mars

HiRISE commonly takes images of recent craters on Mars, which are usually found by the MRO Context Camera where they disturb surface dust. An impact site in this area was first imaged in December 2017.

A year and a half later, the scene looks totally different! Dust has eroded from the surface, probably due to the planet-encircling dust storm from 2018. The dark spots around the fresh craters have vanished because they only affected the dust that has since disappeared. See if you can find the craters in the new image by comparing with the old one.

NASA/JPL/University of Arizona

New Horizons team publishes first Kuiper Belt flyby science results

NASA’s New Horizons mission team has published the first profile of the farthest world ever explored, a planetary building block and Kuiper Belt object called 2014 MU69.

New Horizons team publishes first Kuiper Belt flyby science results
This composite image of the primordial contact binary Kuiper Belt Object 2014 MU69 (nicknamed Ultima Thule) – featured
on the cover of the May 17 issue of the journal Science – was compiled from data obtained by NASA’s New Horizons
spacecraft as it flew by the object on Jan. 1, 2019. The image combines enhanced color data (close to what
the human eye would see) with detailed high-resolution panchromatic pictures [Credit: NASA/Johns
Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko]

Analyzing just the first sets of data gathered during the New Horizons spacecraft’s New Year’s 2019 flyby of MU69 (nicknamed Ultima Thule) the mission team quickly discovered an object far more complex than expected. The team publishes the first peer-reviewed scientific results and interpretations – just four months after the flyby – in the journal Science.

In addition to being the farthest exploration of an object in history – four billion miles from Earth – the flyby of Ultima Thule was also the first investigation by any space mission of a well-preserved planetesimal, an ancient relic from the era of planet formation.

The initial data summarized in Science reveal much about the object’s development, geology and composition. It’s a contact binary, with two distinctly differently shaped lobes. At about 22 miles (36 kilometers) long, Ultima Thule consists of a large, strangely flat lobe (nicknamed «Ultima») connected to a smaller, somewhat rounder lobe (nicknamed «Thule»), at a juncture nicknamed «the neck.» How the two lobes got their unusual shape is an unanticipated mystery that likely relates to how they formed billions of years ago.

The lobes likely once orbited each other, like many so-called binary worlds in the Kuiper Belt, until some process brought them together in what scientists have shown to be a «gentle» merger. For that to happen, much of the binary’s orbital momentum must have dissipated for the objects to come together, but scientists don’t yet know whether that was due to aerodynamic forces from gas in the ancient solar nebula, or if Ultima and Thule ejected other lobes that formed with them to dissipate energy and shrink their orbit. The alignment of the axes of Ultima and Thule indicates that before the merger the two lobes must have become tidally locked, meaning that the same sides always faced each other as they orbited around the same point.

«We’re looking into the well-preserved remnants of the ancient past,» said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. «There is no doubt that the discoveries made about Ultima Thule are going to advance theories of solar system formation.»

As the Science paper reports, New Horizons researchers are also investigating a range of surface features on Ultima Thule, such as bright spots and patches, hills and troughs, and craters and pits on Ultima Thule. The largest depression is a 5-mile-wide (8-kilometer-wide) feature the team has nicknamed Maryland crater – which likely formed from an impact. Some smaller pits on the Kuiper Belt object, however, may have been created by material falling into underground spaces, or due to exotic ices going from a solid to a gas (called sublimation) and leaving pits in its place.

In color and composition, Ultima Thule resembles many other objects found in its area of the Kuiper Belt. It’s very red – redder even than much larger, 1,500-mile (2,400-kilometer) wide Pluto, which New Horizons explored at the inner edge of the Kuiper Belt in 2015 – and is in fact the reddest outer solar system object ever visited by spacecraft; its reddish hue is believed to be caused by modification of the organic materials on its surface New Horizons scientists found evidence for methanol, water ice, and organic molecules on Ultima Thule’s surface – a mixture very different from most icy objects explored previously by spacecraft.

Data transmission from the flyby continues, and will go on until the late summer 2020. In the meantime, New Horizons continues to carry out new observations of additional Kuiper Belt objects it passes in the distance. These additional KBOs are too distant to reveal discoveries like those on MU69, but the team can measure aspects such as the object’s brightness. New Horizons also continues to map the charged-particle radiation and dust environment in the Kuiper Belt.

The New Horizons spacecraft is now 4.1 billion miles (6.6 billion kilometers) from Earth, operating normally and speeding deeper into the Kuiper Belt at nearly 33,000 miles (53,000 kilometers) per hour.

Source: NASA [May 16, 2019]

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Galaxy blazes with new stars born from close encounter

The irregular galaxy NGC 4485 shows all the signs of having been involved in a hit-and-run accident with a bypassing galaxy. Rather than destroying the galaxy, the chance encounter is spawning a new generation of stars, and presumably planets.

Galaxy blazes with new stars born from close encounter
Irregular galaxy NGC 4485, captured by Hubble’s Wide Field Camera 3 (WFC3) [Credit: NASA, ESA;
acknowledgment: T. Roberts (Durham University, UK), D. Calzetti (University of Massachusetts)
and the LEGUS Team, R. Tully (University of Hawaii) and R. Chandar (University of Toledo)]

The right side of the galaxy is ablaze with star formation, shown in the plethora of young blue stars and star-incubating pinkish nebulas. The left side, however, looks intact. It contains hints of the galaxy’s previous spiral structure, which, at one time, was undergoing normal galactic evolution.
The larger culprit galaxy, NGC 4490, is off the bottom of the frame. The two galaxies sideswiped each other millions of years ago and are now 24,000 light-years apart. The gravitational tug-of-war between them created rippling patches of higher-density gas and dust within both galaxies. This activity triggered a flurry of star formation.

This galaxy is a nearby example of the kind of cosmic bumper-car activity that was more common billions of years ago when the universe was smaller and galaxies were closer together.
NGC 4485 lies 25 million light-years away in the northern constellation Canes Venatici (the Hunting Dogs).

This new image, captured by Hubble’s Wide Field Camera 3 (WFC3), provides further insight into the complexities of galaxy evolution.

Source: ESA/Hubble Information Centre [May 16, 2019]

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