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
If you could watch a movie of the planet over the last several million years, you’d see the ice caps advance and retreat: The planet’s climate moves in cycles, with ice ages and interglacial periods alternating. But looking at previous interglacials similar to our own, geophysicists now think that the current mostly ice-less period may be longer than it would have been had a certain species not invented the combustion engine. Specifically, it looks like with amount of greenhouse gases we’ve already spewed into the atmosphere, the next ice age will be delayed. And before you decide that’s a good thing, at the rate we’re currently going, we’re not just pushing off the glaciers for a few geologically insignificant years: the team says that the atmospheric concentration of CO2 would to be at most 240 parts per million (ppm) before glaciation would kick in. Right now, it’s 390 ppm, with no signs of dropping and many signs of continuing to rise. When (and how) the planet’s self-regulation system will kick in isn’t clear, but the long, increasingly hot trip probably isn’t going to be pretty.
Read more at the BBC.
Image courtesy of NASA / Wikipedia
The peripatetic magnetic south pole.
A hundred years after Robert Scott‘s disastrous mission to the South Pole, a pair of Kiwi scientists are traveling to his observation hut today to continue the work he began there: tracking the Earth’s magnetic field. Since 1957, New Zealand has measured the field at Scott’s base every five years, accruing data that, along with measurements from other, more comfortable sites around the world, helps maintain the model used by NATO and nations’ defense departments for navigation.
The planet’s magnetic field needs tracking because it is shifting: the magnetic south pole has been traveling northwestward at a rate of 6 to 9 miles a year for the past century. (The geographic South Pole is somewhere altogether different.) This shift occurs because the mass of molten metal that makes up the Earth’s outer core is in a constant state of turmoil, and the the poles could veer off in another direction at any time. Intriguing, the magnetic field has also been getting weaker since the 1800s. But whether that means the poles will flip at some point in the future—it’s happened before!—or whether it will start getting stronger again very soon is a mystery.
The Laki fissure’s eruption in Iceland was behind tens of thousands of deaths in the 1780s.
What’s the News: Iceland’s busy volcanoes have caused their share of air traffic snafus in Europe lately, but they have the potential to be deadly, not just inconvenient. A new model examining how air quality would change should the volcanoes erupt as spectacularly as they occasionally have in the past suggests that increased particulates in the air could kill more than 140,000 people in Europe in the year following the eruption.