10 Discoveries That Shed Light On Mysteries Of Our Solar System

The Theta Aurora

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Auroras, light shows in the sky more commonly known as the Northern or Southern Lights, usually form when the solar wind collides with the Earth’s magnetic field, also known as the magnetosphere. In other words, it’s a visible way that we see the Sun’s effect on Earth.

Theta auroras may form at higher latitudes, closer to the poles, than typical auroras. The theta aurora can only be seen from above, where it looks like the Greek letter theta (θ). space space science earth science space station science space travel space science earth science space station science

The formation of an aurora depends on the alignment between the interplanetary magnetic field that flows with the solar wind and the Earth’s magnetic field. When the two fields intersect, the Earth’s magnetic field will point north. But if the interplanetary field is pointing south, then the magnetic field lines will point in opposite directions. This causes a process called magnetic reconnection (that isn’t yet well-understood), which realigns the magnetic field lines in a new way.

The new alignment allows the solar wind particles to enter into the Earth’s magnetosphere, a huge magnetic bubble around our planet. When those solar particles flow along the planet’s magnetic field lines and collide with atoms in the Earth’s upper atmosphere, the aurora is born. In this case, the formation is most likely to take place 65–70 degrees north or south of the Earth’s equator.

But theta auroras can happen at higher latitudes if the interplanetary magnetic field is pointing north instead of south. Scientists recently discovered that, when this happened, magnetic reconnection can trap plasma (which is ionized gas) inside the magnetosphere. The trapped plasma becomes hot, and this time, a theta aurora may be born.

The Titan Sand Dune Puzzle

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Titan, which orbits Saturn, is the only moon with a dense atmosphere. Its lakes and seas are made of methane and ethane. This unusual moon also has large, windswept dunes that are hundreds of miles long, over a mile wide, and hundreds of yards high.

At first, the existence of dunes didn’t make sense because we thought Titan only experienced light breezes over its surface. But later research suggested that winds must be stronger than previously believed. NASA’s spacecraft Cassini also sent pictures of the particles that created these dunes.

“It was surprising that Titan had particles the size of grains of sand—we still don’t understand their source—and that it had winds strong enough to move them,” said Devon Burr of the University of Tennessee. “Before seeing the images, we thought that the winds were likely too light to accomplish this movement.”

But scientists were most puzzled by the shape of the dunes. According to data provided by Cassini, the winds usually blew east to west. But the dunes around craters and mountains looked like they’d been created by winds blowing in the other direction. space space science earth science space station science space travel space science earth science space station science

In a NASA high-pressure wind tunnel, Burr and her team spent six yearsrecreating the conditions of wind and sand on Titan. Finally, they found that the wind had to blow at least 50 percent faster than originally believed to create the dunes. Titan’s dense atmosphere made the faster speeds necessary.

Their discovery also explained the shape of the dunes. According to their model, the winds on Titan are usually light, blowing east to west, and are therefore unable to create dunes. But twice every Saturn year, which is equivalent to 30 Earth years, the wind blows faster in the other direction when the Sun crosses Titan’s equator. Burr believes those quick shifts in wind are when the dunes are created, and that accounts for their shape. Cassini may have missed these high wind speeds because they don’t happen often.

Mercury’s Unexpected Volcanoes

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Another NASA spacecraft, MESSENGER, has provided new insights into Mercury’s early planetary history. Originally, scientists believed that Mercury never had active volcanoes because it lacked the volatile compounds in its interior that create the explosions. But pictures from MESSENGER had researchers scrambling to rework their theories.

MESSENGER’s photos showed the presence of pyroclastic ash deposits, which are made from fragments of rock blasted from the vents of volcanoes. So Mercury obviously had volatile compounds. But the data also showed that volcanoes erupted for much of Mercury’s history. space space science earth science space station science space travel space science earth science space station science

That led to another question. Did the volatile compounds in the planet’s interior all explode early in Mercury’s history, or did the explosions occur over a substantially longer period of time?

A research team from Brown University believes the eruptions happened over an extended time frame. They came to that conclusion by looking at the vents of the volcanoes. If the volcanoes had all exploded around the same time, then all the vents would be degraded by about the same amount. But the scientists observed different amounts of degradation, which is consistent with volcanic eruptions over a much longer period of time.

Using the amount of degradation to determine the age of Mercury’s craters, the researchers believe that the volcanic activity probably occurred 1–3.5 billion years ago. That may sound old, but it’s actually geologically young. If the volcanoes had all exploded around the time of Mercury’s formation, the craters would be about 4.5 billion years old.

This information also helps us to figure out how Mercury was formed. According to two popular theories, Mercury used to be bigger but either lost its outer layers when they were fried by the Sun or when they were torn off by a large impact shortly after the planet was formed. Given the new information on volatile compounds, neither of those theories seems likely now.

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