The yellow spots represent icy areas.
Ice? On the planet closest to the Sun? You heard right: Mercury’s northern pole may have craters containing frozen water.
The evidence, presented in three papers published last week in Science, comes from several sources. The Mercury Laser Altimeter, an instrument on the Mercury space probe, MESSENGER, helps scientists map the topography of the planet by firing lasers at its surface and recording the time it takes for the light to return. The instrument also records the intensity of the return beams, and the bright spots reflecting off Mercury’s surface suggest the presence of ice. Read More
Mercury is an odd little planet, tiny but incredibly dense, relatively close by but hard to study via telescope. The MESSENGER probe‘s latest findings, 57 papers presented two days ago at conference, bring new weirdness to our understanding of the planet closest to the Sun.
Take, for instance, the new revelations about Mercury’s core. We always knew that Mercury had a proportionally larger core than Earth does; geologists thought that it might make up a whopping 42% of the planet’s volume, in comparison to Earth’s 17%. The newest estimate, though, blows that out of the water: We now think the number is 85%. To boot, there appears to be an extremely dense layer more than a hundred miles thick encasing the core, perhaps a shell of iron sulfide. That makes the mantle and crust—to use the memorable analogy of a planetary scientist interviewed by Wired—like a mere orange peel on a giant orange of metal.
Another memorable finding: the largest crater on Mercury, Caloris Basin, isn’t actually much of a basin. It seems that the crater’s center gradually rose at some point in the not-too-distant past until it was higher than its edges. This has geologists revising their impressions that Mercury stopped being geologically active 4.5 billion years ago to something more like 2 billion years ago.
Image courtesy of Case Western Reserve University
What’s the News: After firing its thrusters for about 15 minutes on Thursday, NASA’s MESSENGER spacecraft lost enough speed to be pulled in by Mercury’s gravitational field, making it the first probe to orbit the Swift Planet. “Mercury’s secrets, and the implications they hold for the formation and evolution of Earth-like planets, are about to be revealed,” MESSENGER principal investigator Sean Solomon told Slate.
What’s the Olds:
Not So Fast: Don’t expect any stunning images by this weekend: MESSENGER’s first pictures in orbit are slated to arrive toward the end of the month.
The Future Holds: Engineers will continue checking how well the probe is withstanding Mercury’s hot temperatures, with plans of turning on equipment on March 23, and starting scientific studies on April 4. The spacecraft will carry out a one-year survey of Mercury in hopes of using close-up mapping to settle long-held debates, such as whether ice is hiding at the poles.
Image: Science/AAAS, Carnegie Inst.Washington/ Arizona State Univ. / Johns Hopkins Univ. Appl. Phys. Lab. / NASA
It’s no surprise that a chemical as potent as methylmercury harms wildlife when it enters an ecosystem in high concentration. In the case of wetland birds, researchers have found, it can even change sexual orientation, causing males to pair off with other males.
“We knew mercury could depress their testosterone (male sex hormone) levels,” explained Dr Peter Frederick from the University of Florida, who led the study. “But we didn’t expect this.” [BBC News]
Frederick and Nilmini Jayasena examined white ibises from South Florida for their study in the Proceedings of the Royal Society B. They gathered 160 of the birds and broke them up into four groups that ate food laced with different concentrations of methylmercury. Some ate 0.3 parts per million of mercury, some 0.1, some 0.05, and some none at all.
Birds exposed to any mercury displayed courtship behaviour less often than controls and were also less likely to be approached by females when they did. As the level of mercury exposure increased, so did the degree and persistence of homosexual pairing. Males that engaged in homosexual parings were also less likely to switch partners from year to year, which Frederick says ibises tend to do if they have been unsuccessful in mating during their first breeding season. [Nature]
We just won’t let Tycho Brahe be.
A colorful character and a father of modern astronomy, Brahe died in 1601 and was buried at Tyn Church near Prague’s Old Town Square. But the popular explanation for his expiration—a bladder infection—just doesn’t satisfy modern scientists seeking the truth about Tycho. So this week, Danish and Czech scientists (Brahe was Danish but died in Prague) got permission to exhume the long-dead stargazer to find evidence of his true cause of death.
His body has been exhumed before, in 1901. Tests on a sample of hair from his moustache, taken at that time, have been conducted as recently as the 1990s and indicated unusually high levels of mercury. Brahe was also an alchemist and some have suggested that he would have handled mercury and may have administered it to himself as medicine. Others have suggested he was poisoned. [BBC News]
Hello again, Mercury. This week in a trio of papers Science, the scientists behind the Messenger probe released their findings from the craft’s third and final flyby of the planet closest to the sun, which it executed last September. Mercury, they’ve shown once again, is full of surprises—and they’ll get the chance to explore them when Messenger returns and finally enters Mercury’s orbit in March 2011.
Scientists have now mapped 98 percent of the planet by combining the new observations with the first two flybys in January and October 2008, plus the Mariner 10 mission in the ’70s, [said Brett Denevi, coauthor of one of the papers]. The latest flyby filled in a 360-mile-wide gap that had never been imaged before.
“It wasn’t a huge amount of real estate, but there was a lot of really interesting stuff there,” Denevi said. The most exciting features include a 180-mile-wide basin filled with hardened lava, and a crooked bowl surrounded by glass and magma that may be the largest volcanic vent ever identified on Mercury. Together, these features suggest that Mercury had active volcanoes later in its history than scientists had suspected [Wired.com].
The first image above shows a smooth basin dubbed Rachmaninoff, which is one of the smoothest regions seen on Mercury—so smooth that it must have formed from volcanic material in the last billion years or so. The yellowish part in the upper right of this false color image is that volcanic vent.
When NASA’s Messenger space probe swung past Mercury on September 29, it snapped this picture of the innermost planet’s barren and strange landscape. The $446 million probe’s third flyby brought it within 142 miles (228 km) of Mercury’s surface to cover more uncharted terrain, leaving 98 percent of the planet now mapped [SPACE.com].
The images taken and the data recorded during the flyby are the last that will be acquired until Messenger finally slips into orbit around Mercury in 2011. The probe has now completed about three-quarters of its swooping 4.9-billion-mile journey that will eventually bring it into orbit.
Researcher Brett Denevi explains that this enhanced color shot shows a bright area surrounding an irregular depression, with steep sides and an odd shape, “all of which are hallmarks of something like a volcanic vent,” Denevi said [SPACE.com]. The double-ring basin in the center of the photo measures about 180 miles in diameter. It appears to be a relatively young impact crater–researchers believe it formed about 1 billion years ago–and the smooth stuff on the crater floor may be even younger volcanic material.
80beats: Space Probe Soon to Study Mercury’s Comet-Like “Tail”
80beats: Mercury Flyby Reveals Magnetic Twisters and Ancient Magma Oceans
80beats: Brand New Postcards From Mercury, Courtesy of Messenger Space Probe
Today in the innermost region of our solar system, NASA’s Messenger space probe will swoop past Mercury for the third and final time. The maneuver will give scientists a close look at the dense, iron-rich, oddball planet, and will also alter the probe’s trajectory and prepare it to begin orbiting Mercury in March 2011.
As Messenger travels within 142 miles of Mercury at 12,000 miles per hour, the spacecraft’s camera will swivel to stare at a succession of craters and other geological features…. One target will be an old 90-mile-wide crater. Another will be young 13-mile crater and a splash of light-colored soil surrounding it. A third crater of interest has materials of unusual color perhaps produced by violent volcanic eruptions [The New York Times]. When this third flyby is complete, 95 percent of the planet will have been mapped in high resolution.
Engines powered by chemical fuel? How passé. For the spacecraft with truly modern flair, an ion thruster is the only way to go. Such a system might not provide powerful and dramatic bursts of speed, but space agencies around the world are recognizing the benefits of its slow-and-steady approach, which is just what’s needed for cruising between planets.
Ion propulsion works by electrically charging, or ionizing, a gas and accelerating the resulting ions to propel a spacecraft. The concept was conceived more than 50 years ago, and the first spacecraft to use the technology was Deep Space 1 in 1998. Since then … there have only been a few other noncommercial spacecrafts that have used ion propulsion [Technology Review]. However, the technology has a clear advantage over chemical propulsion when it comes to long distance missions, because a very small amount of gas can carry a spacecraft a long way. Astronautics expert Alexander Bruccoleri explains that with chemical propulsion, “You are limited in what you can bring to space because you have to carry a rocket that is mostly fuel” [Technology Review].
Now, a European Space Agency (ESA) probe will use four ion thrusters to scoot all the way to Mercury, the planet nearest to the sun. That mission won’t launch until 2014, but ESA officials say the $37 million propulsion system will be the most efficient yet, and will also be the most ambitious test of the technology to date. The Mercury probe will be launched by a conventional rocket, and will continue to use chemical propulsion until it’s out of Earth orbit. When it begins its six-year cruise to Mercury, though, its ion thrusters will kick in. The system will draw electricity from solar panels; as the xenon ions pass through the electrified grids they accelerate to up to 50km a second (31 miles per second) and shoot from the rear in a parallel beam. On Earth, at sea level, the thrust would be just enough to lift a pound coin. In space, however, the same thrust will create a much much bigger lift [Telegraph].
Is planetary Armageddon just a matter of time? Will Earth meet its fiery doom when the orbits of the planets in our solar system become destabilized, leading Mars, Mercury, or Venus to crash into our home turf? A new study predicts that there is indeed a very slim possibility that such a cataclysm will rock our world, but notes that the possible collisions wouldn’t happen for more than 3 billion years, by which time humans may be long gone. “I see the results as a case of the glass being 99 percent full and 1 percent empty…. While it’s possible that a collision could occur billions of years from now, it’s actually very unlikely” [SPACE.com], says Gregory Laughlin, an astronomer who wasn’t involved in the current research.
Astronomers had thought that the orbits of the planets were predictable. But 20 years ago, researchers showed that there were slight fluctuations in their paths. Now, the team has shown how in a small proportion of cases these fluctuations can grow until after several million years, the orbits of the inner planets begin to overlap [BBC News]. The researchers simulated the interactions of the eight major planets, Pluto, and the moon over the course of 5 billion years, up until our sun is expected to expand into a red giant. The simulation, described in the study published in Nature, covered more than 2,500 possible futures.