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5 Cratered Facts About Mercury

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An enhanced-color composite image of Mercury's Caloris basin. Lavas appear orange, and blue areas are likely the original basin floor. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


by Alex Carter

Mercury is the closest planet to the sun, and you would be forgiven for thinking it’s just a boring lump of rock. After all, there’s nothing interesting on it like aliens or places to drink. Still, Mercury is probably a more interesting place than you think...


Although you would be forgiven for thinking Mercury, being the closest planet to the Sun, is one of the hottest places in the solar system, it in fact is subject to enormous temperature fluctuations. Some regions reach 800°F, but without an atmosphere to retain heat, Mercury’s poles and nightside of the planet plunge well below even the coldest temperatures recorded on Earth. With some regions never getting above -279°F, conditions are perfect for ice to form. Mercury’s regolith is home to possibly a trillion tons of ice, which would make it one of the wettest places in the solar system.

Fitting, then, that the ancient Chinese called it the Water Star.


In the 19th century, scientists were smug in the knowledge that they knew everything there was to know. There were of course a couple of curiosities that they could not understand, one being the precession in the orbit of Mercury. That is to say, Mercury goes around the Sun in an ellipse rather than in a circle, and the ellipse changed the direction it was pointing from time to time. It was thought that there must be a new planet between Mercury and the sun that was changing its orbit—the planet Vulcan. But despite trying, the planet could not be observed.

Albert Einstein eventually disproved the theory of Vulcan via the general theory of relativity. Rather than looking for an external cause, Einstein showed that Mercury was doing exactly what it should do, and that gravity was just acting in ways no one had known it could. Mercury is so close to the Sun that not only is it pulled around the Sun, space itself is too. Were it not for Mercury demonstrating this effect, Einstein probably would not have been so readily believed.

Incidentally, the other curiosity was the photoelectric effect, which needed quantum mechanics to explain. That, not relativity, was what Einstein won his Nobel Prize for.


After six years orbiting the planet, NASA’s MESSENGER probe ran out of fuel in 2014 and could no longer correct its course. As its orbit decayed, it got closer to the planet, and much faster. The resulting crash into Mercury a year later occurred at more than 8000 mph and left a crater more than 50 feet wide. That makes it easily the biggest humanmade crater anywhere in the universe … apart from those on Earth, obviously.


Mercury orbits so close to the Sun that the conventional ideas of days and years don’t really make much sense. Mercury’s rotation (remember, rotation on a planet's axis causes its days) and orbit (which causes its years) are linked through gravity more tightly than Earth. In fact, Mercury rotates three times on its axis every two years. This makes each Mercury day—as in sunrise to sunset and back to sunrise—last two of its years. It’s a weird day, too: The Sun rises, goes backwards in the sky to set, rises again, then finally sets a year later. The next year, from the perspective of Mercury, the Sun would appear to move in the opposite direction.


Mercury’s small size means it has no permanent atmosphere, just a thin layer called an exosphere; its gravity is too weak to hold onto any gas in the wake of the strong solar wind. However, it does have a remarkably strong magnetic field, which means it keeps a hold of whatever ions come its way. There are a lot of ions in that part of space.

So while planets such as Earth are nice and oxygen filled, Mercury’s atmosphere contains the kind of things planets normally don’t hang on to, including ions of magnesium, calcium, sodium (you may remember from chemistry class that those are the ones that explode in water), as well as unusual ions of water. Mercury may smell like wet, metallic burps. 

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Gregory H. Revera, Wikimedia Commons // CC BY-SA 3.0
Study Suggests There's Water Beneath the Moon's Surface
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Gregory H. Revera, Wikimedia Commons // CC BY-SA 3.0

Astronauts may not need to go far to find water outside Earth. As CNN reports, Brown University scientists Ralph E. Milliken and Shuai Li suspect there are significant amounts of water churning within the Moon’s interior.

Their findings, published in the journal Nature Geoscience, lean on the discovery of glass beads encased in the Moon’s volcanic rock deposits. As recently as 100 million years ago, the Earth’s moon was a hotbed of volcanic activity. Evidence of that volatile time can still be found in the ancient ash and volcanic rock that’s scattered across the surface.

Using satellite imagery, the researchers identified tiny water droplets preserved inside glass beads that formed in the volcanic deposits. While water makes up a small fraction of each bead, its presence suggests there’s significantly more of it making up the Moon’s mantle.

Milliken and Li aren't the first scientists to notice water in lunar rocks. In 2008, volcanic materials collected from the Moon during the Apollo missions of 1971 and 1972 were revealed to contain the same water-flecked glass beads that the Brown scientists made the basis of their recent study. They took their research further by analyzing images captured across the face of the Moon and quickly saw the Apollo rocks represented a larger trend. "The distribution of these water-rich deposits is the key thing," Milliken said in a press statement. "They're spread across the surface, which tells us that the water found in the Apollo samples isn't a one-off. Lunar pyroclastics seem to be universally water-rich, which suggests the same may be true of the mantle."

The study challenges what we know about the Moon's formation, which scientists think occurred when a planet-sized object slammed into the Earth 4.5 billion years ago. "The growing evidence for water inside the Moon suggests that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the Moon had completely solidified," Li said. "The exact origin of water in the lunar interior is still a big question."

The findings also hold exciting possibilities for the future of space travel. NASA scientists have already considered turning the Moon into a water station for astronauts on their way to Mars. If water on the celestial body is really as abundant as the evidence may suggest, figuring out how to access that resource will definitely be on NASA's agenda.

[h/t CNN]

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Bruce Weaver / Stringer / Getty Images
NASA Is Posting Hundreds of Retro Flight Research Videos on YouTube
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Bruce Weaver / Stringer / Getty Images

If you’re interested in taking a tour through NASA history, head over to the YouTube page of the Armstrong Flight Research Center, located at Edwards Air Force Base, in southern California. According to Motherboard, the agency is in the middle of posting hundreds of rare aircraft videos dating back to the 1940s.

In an effort to open more of its archives to the public, NASA plans to upload 500 historic films to YouTube over the next few months. More than 300 videos have been published so far, and they range from footage of a D-558 Skystreak jet being assembled in 1947 to a clip of the first test flight of an inflatable-winged plane in 2001. Other highlights include the Space Shuttle Endeavour's final flight over Los Angeles and a controlled crash of a Boeing 720 jet.

The research footage was available to the public prior to the mass upload, but viewers had to go through the Dryden Aircraft Movie Collection on the research center’s website to see them. The current catalogue on YouTube is much easier to browse through, with clear playlist categories like supersonic aircraft and unmanned aerial vehicles. You can get a taste of what to expect from the page in the sample videos below.

[h/t Motherboard]


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