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OUT OF THIS WORLD | Science Pics of the Week

NASA reveals the many fascinating faces of Pluto and Charon

Scott Sutherland
Meteorologist/Science Writer

Friday, November 20, 2015, 5:55 PM - A fascinating look at a day on Pluto and Charon, spotting bright "invisible" loops on the Sun and watching a passing storm stir up Lake Erie into a murky mess. It's Science Pics of the Week!

Spending a day with distant Pluto and Charon

NASA's New Horizons spacecraft is currently speeding towards its next encounter in the Kuiper Belt, but here on Earth, we are still marveling over the images it sent back from its fly through the Pluto system.

The latest treats released by NASA are images showing a full day on both Pluto and Charon.

This "ring" of Plutos shows the best images of the icy dwarf planet's sunward side as New Horizons flew past. They represent a full Plutonian day. Credits: NASA/JHUAPL/SwRI

According to NASA:

Pluto’s day is 6.4 Earth days long. The images were taken by the Long Range Reconnaissance Imager (LORRI) and the Ralph/Multispectral Visible Imaging Camera as the distance between New Horizons and Pluto decreased from 5 million miles (8 million kilometers) on July 7 to 400,000 miles (about 645,000 kilometers) on July 13. The more distant images contribute to the view at the 3 o’clock position, with the top of the heart-shaped, informally named Tombaugh Regio slipping out of view, giving way to the side of Pluto that was facing away from New Horizons during closest approach on July 14. The side New Horizons saw in most detail – what the mission team calls the "encounter hemisphere" – is at the 6 o’clock position.

This corresponding "ring" of Charons gives the best images of this icy dwarf planet's sunward side as New Horizons flew past. They represent a full Charonian day. Credits: NASA/JHUAPL/SwRI

According to NASA:

Charon – like Pluto – rotates once every 6.4 Earth days. The photos were taken by the Long Range Reconnaissance Imager (LORRI) and the Ralph/Multispectral Visible Imaging Camera from July 7-13, as New Horizons closed in over a range of 6.4 million miles (10.2 million kilometers). The more distant images contribute to the view at the 9 o’clock position, with few of the signature surface features visible, such as the cratered uplands, canyons, or rolling plains of the informally named Vulcan Planum. The side New Horizons saw in most detail, during closest approach on July 14, 2015, is at the 12 o’clock position.

Some of these faces are blurrier than others due to New Horizon's distance from the binary pair as the images were snapped. To get an idea of the difference, here is a comparative image, showing tiny, 8 million km away Pluto and Charon (centre) versus how they looked at just 645,000 kilometers away, on July 13.

Credits: NASA/JHUAPL/SwRI/S.Sutherland

The fact that the "far side" views of both are as clear as they are is simply a marvel of technology and digital image processing, and those are likely to be the clearest images of those hemispheres that we will see for some time to come.

Bright "invisible" loops on the Sun

Wait, what? How can something be invisible and bright at the same time?

According to NASA (emphasis mine):

Two active regions sprouted arches of bundled magnetic loops in this video from NASA’s Solar Dynamics Observatory taken on Nov. 11-12, 2015. Charged particles spin along the magnetic field, tracing out bright lines as they emit light in extreme ultraviolet wavelengths. About halfway through the video, a small eruption from the active region near the center causes the coils to rise up and become brighter as the region re-organizes its magnetic field. This video was taken in extreme ultraviolet wavelengths of 171 angstroms, typically invisible to our eyes but colored here in gold.

Put on a pair of special aluminized mylar glasses, use a piece of #14 welder's glass, or construct a pinhole projector to view the Sun (DON'T look at it any other way or you could damage your eyes), and you'll see the photosphere - the 100 km thick layer that sports a rich yellow hue and shows off the numerous sunspots that track across the face of the Sun. There is activity on the Sun that goes far beyond our limited band of visible light, though.

While the view we see in that band corresponds to temperatures of about 5,700 Kelvin, the 171 angstrom view from SDO filters out everything except light that's emitted by particles with temperatures around 1 million Kelvin. This intense ultraviolet light is absorbed by the ozone layer long before it could make it to the ground, but even above the atmosphere it would be completely invisible to us if it weren't for the technology in place on SDO and its "cousins" - the Solar and Heliospheric Observatory (SOHO) and the twin Solar Terrestrial Relations Observatories (STEREO A and STEREO B).

Weather turns Lake Erie from green to murky brown

Credit: NASA Aqua/Terra MODIS

Lake Erie has something of an algae problem. Each year, the western end of the lake experiences a massive bloom of toxic algae known as cyanobacteria. This year, forecasters were anticipating a near-record year for the annual bloom's extent, but their projections didn't go far enough. 2015 turned out to have the most extreme algal bloom ever, beating out the extent of the 2011 bloom. The only positive side to what happened this year was that the bloom spread into the central portion of the lake, rather than accumulating near shorelines. Thus, it did not have the same impact on local residents as was seen in 2011.

The animation above shows the lake, as seen by NASA's Aqua and Terra satellites, from November 2 to November 16, 2015. At the start of the animation, the swirls of lighter colour in the water are a mix of algae (green) and sediment (brown/white). As the animation progresses, this mixture swirls around in the lake currents. Watch closely after the last band of obscuring cloud passes by, though - from the weather system that swept through southern Ontario on November 10.

The strong winds blowing across the lake from that system stirred up the shallow lake water, mixing the algae deeper down while churning up sediment from the bottom up to the surface. After the clouds pass, the lake is transformed into a murky, swirling mess.

While the lake certainly doesn't look very good in those final frames of the animation (except the the geode-like pattern at the eastern end), these sediment events actually help to keep algal blooms under control.
According to NOAA forecasters, based on what was seen in previous years, this record bloom should have taken quite awhile to diminish. However, strong winds from two major weather systems in early September stirred the lake up enough that the bloom was prevented from growing larger. At the same time, the combination of algae mixing down into the deeper waters and sediment being drawn up to the surface weakened the existing bloom significantly, causing it to decline earlier than expected. If those storms had not stirred up the lake, who knows how large this bloom could have grown.

Sources: NASA | JHUAPL | NASA SDO | NASA Worldview | NOAA (pdf)

Related Video: Science@NASA presents The Good, The Bad and The Algae

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