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New Evidence Points To Icy Plate Tectonics On Europa (gizmodo.com)
According to new research published today in Journal of Geophysical Research: Planets, Europa has what it takes to support plate tectonics. "Using computer models, a team lead by Brown University planetary scientist Brandon Johnson was able to demonstrate the physical feasibility of icy plates driving deep into the icy interior in a processes similar to what's seen on Earth," reports Gizmodo. "Excitingly, this same process could be delivering important minerals to the ocean below, heightening the moon's status a potentially habitable world." From the report: Europa has surface features reminiscent of Earth's mid-ocean ridges. For astronomers, this hinted at geological processes akin to subduction zones, where, on Earth, tectonic plates slide underneath another, sinking deep into the planet's interior. Several years ago, researchers Simon Kattenhorn and Louise Prockter posited this explanation when they noticed that a 20,000 square-kilometer (7,722 square-mile) chunk of ice had mysteriously disappeared from Europa's surface. Their explanation was that Europa's surface, like a gigantic jigsaw puzzle, is composed of tectonic plates, and that occasionally a plate of ice will sink beneath the other into warmer layers below. But this observational evidence of extension and spreading needed to be supported by geophysical reality. To that end, Johnson's team ran a computer simulation to see if it was possible for ice to sink in this way.
On our planet, subduction is primarily driven by differences in temperature between a descending slab and the surrounding mantle. Dense crustal material features a negative buoyancy that drives it down into the mantle. The Brown University scientists figured a similar thing happens on Europa, but with ice. In the case of Europa, the researchers surmised that the moon has two frozen layers -- an outer lid of very cold ice that sits above a layer of slightly warmer convecting ice. Their models showed that subduction is indeed possible in this alien environment, but only if the outer shell contains varying amounts of salt. This added ingredient provides the necessary density differences for a slab to conduct.
On our planet, subduction is primarily driven by differences in temperature between a descending slab and the surrounding mantle. Dense crustal material features a negative buoyancy that drives it down into the mantle. The Brown University scientists figured a similar thing happens on Europa, but with ice. In the case of Europa, the researchers surmised that the moon has two frozen layers -- an outer lid of very cold ice that sits above a layer of slightly warmer convecting ice. Their models showed that subduction is indeed possible in this alien environment, but only if the outer shell contains varying amounts of salt. This added ingredient provides the necessary density differences for a slab to conduct.
The earliest claimed fossilized lifeforms on earth are as old as old as 4.28 billion years old. it suggests an almost instantaneous emergence of life after oceans formed 4.4 billion years ago. Obviously Europa doesn't have the same conditions as early earth but perhaps the Abiogenesis is simply slower instead of impossible under those conditions and Europa has had plenty of time. We just don't know
Some sure, but the other moons of jupiter would be jet black even in their craters if it was any significant amount. Since there're not, it obviously isn't.
Unfortunately, the math says otherwise.
The Earth - the one example of intelligent life in the Milky Way known to humanity - is ~4.5 billion years old, and it's taken ~4 billion years of that time to have us evolve on it to the point we can post about it on Slashdot. We don't know, however, if that's an unusually long time, or an unusually short time.
Hopefully it's long or average, because our star is near the end of it's current Earth-supporting phase. If you assume you need a Sun-like star (smaller gets you a longer-lasting star, but the habitable zone gets closer to requiring planets to be tidally locked, and stellar temperament becomes a problem, too), then you pretty much want to know people can pop up on an orbiting rock in less than 4 billion years.
Anyway, at speeds we can reach with our technology, it would take around 5 million years to cross the galaxy. 5 million years is peanuts compared to the 4 billion years life has been on Earth so far. Now consider there are probably ~10 billion potentially habitable worlds in the Milky Way based on our current models.
Only ONE of those 10 billion worlds has to have intelligent life begin to colonize the galaxy a mere 5 million years before we started talking about it to arrive by tea time tomorrow.
And the Sun wasn't the first star of its class to be born. There's at least one similar star we know of that's over 11 billion years old, which potentially means there's an extra 7 billion years of leeway for aliens to set up shop everywhere. Well, not everywhere - obviously if they were zipping around the Milky Way more than 4 billion years ago, Earth would just have been a hot damp rock. On the other hand, you'd expect that with the extra lead time, they'd be around pretty much every star in the sky and we'd have seen SOMETHING by now.