Aurora on May 24, 2010. Taken from the ISS.

Finding and reporting auroras

When the solar wind interacts with Earth’s magnetic field in a specific way, the stunning light shows known as auroras happen. And while satellites monitor the Sun for occurrences such as coronal mass ejections (CMEs) that could produce auroras here on Earth, understanding where and when an aurora will take place has proven challenging.

A new project, funded by the National Science Foundation (NSF), called Aurorasaurus, allows citizens around the world to track auroras and report on their progress. Visitors to the Aurorasaurus website can see where an aurora is happening in real-time, let other Aurorasaurus visitors know of an aurora’s existence, and receive early warnings when an aurora is likely to happen in their Earth-neighborhood.

And the project provides more than just skywatching information. Therese Moretto Jorgensen of NSF explains, “There's a close relationship between auroras and the magnetic variations that pose a threat to the power grid. A better understanding of when and where auroras happen will help us develop models that can forecast these potentially hazardous events.” –Molly Michelson

A Short Total Lunar Eclipse

On the morning of Saturday, April 4, a total lunar eclipse will be seen as the full Moon passes through Earth’s shadow. Unfortunately for East Coast skywatchers, totality will occur after moonset, but they will see the early partial phases. The farther west American observers are located, the more they’ll see, with moonwatchers on the West Coast able to see totality—when the Moon is completely immersed in the umbra, or the dark center, of our planet’s reddish shadow—but just barely. Earth’s shadow consists of a dark center, or umbra, and a fainter portion, or penumbra. The Moon will pass just inside the edge of the umbra and start to exit only minutes after it has entered, producing the shortest period of totality for any lunar eclipse this century.

For observers on the West Coast, first contactwhen the Moon first touches the umbra occurs at 3:16 a.m. PDT. Totality begins at 4:58 a.m. and ends at 5:03 a.m. PDT. Estimates of the duration of totality range from 5 to 12 minutes, depending on how the edge of the fuzzy umbral shadow is defined. In fact, being barely within the umbra, the Moon’s northernmost edge may still look relatively bright. Fourth contactwhen the Moon exits the umbrais at 6:45 a.m. PDT.

This is the first of two total lunar eclipses in 2015 and the third of a series of four total lunar eclipses in a row, without any partials, known as a tetrad. The next total lunar eclipse will occur on September 28, 2015. For more on lunar eclipses in general and details on observing them, check out the Academy’s recent “How to Observe a Lunar Eclipse” video. -Bing Quock

Curiosity Testing Martian Atmosphere

NASA announced this week that the Curiosity rover is testing the martian atmosphere for xenon, in order to better understand the depletion of Mars’s atmosphere.

Although Curiosity, which landed on Mars in August 2012, is known for studying and sampling rocks and geology in Gale Crater, it also regularly analyzes air on the planet with the Sample Analysis at Mars (SAM) lab. Last year, the team announced the rover detected evidence of methane in the atmosphere, potentially indicating activity below the Martian surface.

Evidence suggests that long ago Mars was a very different place from the cold, dry, thin-atmosphered world see today. Generations of orbiters and rovers, including Curiosity, have collected data that suggest a vast ocean covered much of Mars, some 3 to 3.5 billion years ago. At that time, Mars would have also had a stronger magnetic field and thicker atmosphere. Over time, the latter two are thought to have stripped away, and Mars’s water evaporated into space or froze near the ice caps.

But why test for xenon?

Because it comes in so many varieties! Xenon has nine naturally-occurring isotopes, each with a slightly different mass. As Mars loses its atmosphere, gases with lighter atoms and molecules escape more rapidly than those with heavier atoms and molecules. Xenon is a pretty massive atom to begin with, but its nine variants provide a finely-tuned set of diagnostics for scientists to study.

“Xenon is a fundamental measurement to make on a planet such as Mars or Venus, since it provides essential information to understand the early history of these planets and why they turned out so differently from Earth,” explains Melissa Trainer.

Measuring xenon’s special characteristics tells more about the history of the loss of the Martian atmosphere. The slightly more massive isotopes should escape a little more slowly than their less massive counterparts, so the ratios of the nine isotopes help disentangle the history of the martian atmosphere. Specifically, more can be learned about the process by which the layers of atmosphere were stripped off of Mars than using measurements of other gases. -Elise Ricard

Dawn over Ceres

On March 6, NASA’s Dawn spacecraft arrived at Ceres, making it the first vehicle to orbit two extraterrestrial bodies: its previous stop was the asteroid Vesta. Launched in 2007 and now making humankind’s first-ever encounter with a dwarf planet, it may offer a preview of what New Horizons will see when it arrives at the reclassified dwarf planet Pluto in July.

So why haven’t we seen any new pictures since then? The orbit insertion process has taken longer than originally planned, due to an unforeseen radiation anomaly in September that affected the spacecraft’s ion thrust control circuitry. As a result, Dawn was pointed slightly off-target. To compensate, operators designed a new approach to the dwarf planet, replacing the original direct spiral path with a long, narrow loop that first overshot its target, then used Ceres’s gravity to pull the spacecraft back into its intended circular orbit. For much of that loop—which is now nearly completed—Dawn is on the shadowed side of Ceres, so anything it sees as it looks down to the surface is dark, not conducive to taking good pictures.

With the completion of its detour on April 9, Dawn will be in a circular orbit around the largest body in the asteroid belt and looking at its sunlit side, ready to reveal its long-hidden secrets. -Bing Quock

The formation of gas giant planets

Why do distant gas giants—such as Jupiter and Saturn—exist in our solar system and other systems?

Scientists understand that planetary systems are born in disks of gas, dust, and rocky fragments that surround newly formed stars when the debris assembles into larger fragments that become planetary “embryos.” But most computational models show smaller embryos migrating toward the central star. This migration is thought to limit the formation of gas giant planets located at Earth’s distance from the Sun and beyond, in contrast with actual observations.

But in this week’s Nature, Universidad Nacional Autónoma de México’s Frédéric Masset and colleagues identify a safety net that prevents inward migration of these planetary embryos. Their computer simulations demonstrate that planetary heating, which occurs as the embryos take in matter and grow, produces a force that counteracts inward migration, thereby allowing giant planets to form. Learning the details of this heating process may help us to gain a deeper understanding of giant planet formation in general as well as the specific conditions that gave rise to our solar system. –Molly Michelson

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