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+--- Thread: Proxima Centauri b: The habitability question + Volcanoes of mud erupt from Ceres (/thread-6151.html)
Proxima Centauri b: The habitability question + Volcanoes of mud erupt from Ceres - C C - Sep 17, 2018
Proxima Centauri b: The Habitability Question
https://www.centauri-dreams.org/2018/09/17/proxima-centauri-b-the-habitability-question/
EXCERPT: Proxima Centauri b is back in the news, although I’ll confess that in my case, it’s rarely out of my thoughts — I’ve been obsessed with the Alpha Centauri system since my youth. The latest comes through work by Anthony Del Genio and colleagues (NASA GSFC), who describe in Astrobiology their new simulations with regard to potential habitability.
You’ll recall the issues here. A planet this close to its host star may well be tidally locked, with one side always facing the M-dwarf Proxima Centauri. Martin Turbet (Sorbonne Universités, Paris) and colleagues described possible climates on Proxima b in a 2016 paper, using a 3D climate model (GCM) to simulate the atmosphere and water cycle of the planet for its two possible rotation modes, a 1:1 and a 3:2 spin resonance (in other words, gravitational forces could keep Centauri b locked to Proxima or rotating 3 times for every 2 orbits of the star).
The Solar System offers analogues: The Moon is in a 1:1 spin resonance with the Earth, while Mercury is in a 3:2 spin resonance with the Sun. What Del Genio and company bring to the table is a model that incorporates these resonances and a global climate model but also includes the effects of an ocean that can transfer heat from one side of the planet to another.
The addition of this dynamic ocean modeling gets us to an interesting outcome: Rather than, as with the Turbet paper, finding an entirely frozen dark side, with a star-facing side that has at least some potential for a sea, Proxima b may have conditions allowing for an equatorial zone of liquid water even on the dark side, with large open ocean possible elsewhere.
This result improves the odds on habitability, as Del Genio is quoted as saying in an article called The Closest Exoplanet to Earth Could Be “Highly Habitable.” An ocean-covered Proxima b with an atmosphere like Earth’s could have open oceans that extend into the dark side, at least at low latitudes, and this turns out to be true both for synchronous rotation and a 3:2 spin-orbit resonance with a somewhat eccentric orbit....
MORE: https://www.centauri-dreams.org/2018/09/17/proxima-centauri-b-the-habitability-question/
Volcanoes of Mud Erupt From Giant Asteroid Ceres
http://blogs.discovermagazine.com/d-brief/2018/09/17/ceres-ice-volcano-mud-asteroid-cryovolcanism/
EXCERPT: . . . There are two types of volcanism in the solar system, typically: the kinds of magma eruptions seen on Earth and Jupiter’s moon Io, where heated rock wells up from the core to the surface. And then there’s the kind of volcanism seen on Europa and Enceladus, where large plumes of frozen water erupt. Scientists call this cryovolcanism. Hanna Sizemore, a Planetary Science Institute research scientist and author on the paper, says Ceres’ volcanoes are a weird mix of the two.
“The big difference on Ceres is that you’re in this hybrid between the inner rocky solar system and the icy outer solar system,” she says. That means that while water may be a driving mechanism for the volcanoes, the actual material could include rock, salt, and heated material from the interior of Ceres, which is both a rocky and an icy world at once. When those volcanoes explode, “It would probably look superficially like lava extrusion on the earth, but it would be mud oozing out of cracks or fissures on the surface,” Sizemore says.
Sizemore says a new cryovolcano appears on Ceres roughly once every 50 million years, as indicated by data from the Dawn spacecraft, which has orbited Ceres for around three years. The craft has seen a series of “domes” dotting the world that have similar proportions to mountains, but are made of ices that have since settled after their volcanically active period ended, leveling them out a little....
MORE: http://blogs.discovermagazine.com/d-brief/2018/09/17/ceres-ice-volcano-mud-asteroid-cryovolcanism/