A Double Ringed Basin on Mercury
Credit: NASA/JHU APL/CIW
Posted on 10/07/2009 5:39:22 AM PDT by sig226
Explanation: What created the internal second ring of this double ringed basin on Mercury? No one is sure. The unusual feature spans 160 kilometers and was imaged during the robotic MESSENGER spacecraft's swing past our Solar System's innermost planet last week. Double and multiple ringed basins, although rare, have also been imaged in years past on Mars, Venus, Earth, and Earth's Moon. Mercury itself has several doubles, including huge Caloris basin, Rembrandt basin, and enigmatic Raditladi basin. Most large circular features on planets and moons are caused initially by a forceful impact by a single asteroid or comet fragment. Since it is unlikely that a second impact would occur right in the center of the first, large double rings are usually attributed to a subsequent volcanic lava flow inside the impact crater. Possibly, though, a second ring could be caused by the melting and flowing of material upon impact. One clue to the origin of the above-imaged double ring is that the basin center appears much smoother than the region between the rings. MESSENGER has now completed its last flyby of Mercury but will return and attempt to enter orbit in 2011 March.
Any evidence of a double ring impact on earth?
Mercury being so close to the sun, it may have stayed molten (or partially molten) longer. Since most of the double-ring basins are old (witness the many smaller craters overlaying the one in the pic), those double rings may be ripples formed when impactors struck a viscous or nearly-viscous surface that was right at the phase-change threshold. The energy of the impact may have heated the surface just enough to ripple, and it cooled again while the ripples were still separate.
In my opinion, Mercury is our most boring planet. Not that it isn’t of scientific value, I just can’t get excited about it.
Looks like a great place to mine for heavy metals.
Those were some BIG raindrops! LOL
Like a "robin hood" arrow.
Gleeb: “Zork, did you do donuts on Mercury?”
Zork: Who me?
Gleeb: I’m telling Mom.
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Doublet impacts are common.
http://www.boulder.swri.edu/~bottke/clearwat.jpg
“Nearly 10% of the largest craters on Earth (including East and West Clearwater Lake in Canada, shown above) are doublets, formed by the nearly simultaneous impact of objects of comparable size.”
http://www.boulder.swri.edu/~bottke/
Crater chains:
http://www.boulder.swri.edu/~bottke/crater_chain/chain.html
I thought double rings were a sometimes feature of large boloid impact craters, including here on Earth.
Thank you, I just got back to this.
Yeah, a single impact can cause that. Has to do with the impact zone and what it’s made of. :’)
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