The traditional story about the formation of our beautiful moon is the single impact theory. But the early solar system was a violent, chaotic place. There’s room for more than one titanic collision. And some new analysis suggests multiple large impacts may explain the modern day Earth-moon system even better in some key ways:
The new model is consistent with science's current understanding of the formation of Earth. In its last stages of the growth, Earth experienced many giant impacts with other bodies. Each of these impacts contributed more material to the proto-Earth, until it reached its current size. "We believe Earth had many previous moons," said Prof. Perets, who added that, "a previously formed moon could therefore already exist when another moon-forming giant impact occurs."
The tidal forces from Earth could cause moons to slowly migrate outwards (the current Moon is slowly doing that at a pace of about 1 cm a year). A pre-existing moon would slowly move out by the time another moon forms. However, their mutual gravitational attraction would eventually cause the moons to affect each other, and change their orbits. "It's likely that small moons formed through the process could cross orbits, collide and merge," said lead author Prof. Rufo. "A long series of such moon-moon collisions could gradually build-up a bigger moon -- the Moon we see today.”
- Speaking of collisions, we just missed being part of a comparatively safe one earlier this week, and while we can’t go back in time to watch the great impacts, there might be an even bigger one between two stars that it could be easily visible from Earth in 2022:
This "death spiral" will likely end in a "lumnious red nova." As implied by its name, these types of stellar explosions are red in color, and are thought to be caused by this kind of binary collision. The nova would increase the stars' brightness by about 1,000 times, and would theoretically become visible to the naked eye on Earth.
Last week, British scientists announced a disturbing finding — a crack in the Larsen C ice shelf in the Antarctic Peninsula had dramatically accelerated its spread, increasing 11 miles in length in the space of a month. This means the floating ice shelf, which is nearly as big as Scotland and the fourth largest of its kind in Antarctica, is poised to break off a piece nearly 2,000 square miles in size, or over 10 percent of its total area. An ice island the size of a small U.S. state would then be afloat in the Southern Ocean.
Russia needs clear economic policies to prevent shocks from oil prices, though stability is expected at $40 per barrel, a development minister said. The Central Bank of Russia in late December reported a net contraction for full-year 2016, though the level of decline was less severe in the latter half of the year. The oil-dependent economy faced dual strains from the low price of oil and economic sanctions, but Russian Minister of Economic Development Maxim Oreshkin told business daily Kommersant the situation is improving as crude oil prices increase.