Mercury lost 65% of its original mass from a collision (?)

[silylene old]

Interesting study:<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><b>Asteroid Crash on Mercury Splattered Earth, Study Says</b><br />Adrianne Appel<br />for National Geographic News<br /><br />April 4, 2006<br />An asteroid collided with the still-forming Mercury some 4.5 billion years ago, sending chunks of the planet hurtling through space, scientists say. <br /><br />What's more, the collision was big enough to send up to 16 million billion tons (16 quadrillion tons) of Mercury's rocky material tens of millions of miles to Earth, new computer simulations suggest. <br /><br />Some scientists believe that Mercury was much larger as it was forming than it is today. It had a lighter, rockier outer layer, similar to that of Earth's, which was blasted away in the great crash, they say. <br /><br />This would explain why Mercury is so different from its neighbors Venus and Earth. Mercury is very heavy for its size, due to an unusually large amount of iron, scientists believe. ......<br />At the end of this hours-long process, Mercury would have been left at 35 percent of its original size. <br /><br />"You've lost more [of Mercury] than what is left,'' Horner said. <br />.....<br /><br /><p><hr /></p></p></blockquote> read the rest here: http://news.nationalgeographic.com/news/2006/04/0404_060404_mercury_2.html <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[CalliArcale]

Very interesting indeed. So perhaps Mercury's enormous density is really just because it's had most of its exterior stripped away. It's just a naked core.<br /><br />MESSENGER can't get there soon enough, in my opinion.... <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[bonzelite]

<i>in my opinion</i> i will maintain that Mercury <i>may have been</i> a gas giant.

 

[earthseed]

Was the impactor an asteroid, or perhaps a sister body to Mercury at one of its Lagrange points? Maybe it was the same process proposed to have formed the Earth's moon.<blockquote><em>The current standard theory of the origin of the Moon is that the Earth was hit by a giant impactor the size of Mars causing ejection of iron poor impactor mantle debris that coalesced to form the Moon. But where did this Mars-sized impactor come from? Isotopic evidence suggests that it came from 1AU radius in the solar nebula and computer simulations are consistent with it approaching Earth on a zero-energy parabolic trajectory. But how could such a large object form in the disk of planetesimals at 1AU without colliding with the Earth early-on before having a chance to grow large or before its or the Earth’s iron core had formed?<br /><br />We propose that the giant impactor could have formed in a stable orbit among debris at the Earth’s Lagrange point L4 (or L5). We show such a configuration is stable, even for a Mars-sized impactor. It could grow gradually by accretion at L4 (or L5), but eventually gravitational interactions with other growing planetesimals could kick it out into a chaotic creeping orbit which we show would likely cause it to hit the Earth on a zero-energy parabolic trajectory. This paper argues that this scenario is possible and should be further studied.</em></blockquote>This may be a fundamental part of planet formation.

 

[thepiper]

<font color="orange">So perhaps Mercury's enormous density is really just because it's had most of its exterior stripped away. It's just a naked core.</font><br /><br />That sounds very much like what I said about Mercury on a different thread, only I identified the "remains" as well.<br /><br />Why, you can even see the "exit wound"... <img src="/images/icons/wink.gif" />

 

[astroguard]

<blockquote><font class="small">In reply to:</font><hr /><p><b>borman</b> wrote:<br />If the moon formed before the collision, maybe evidence is still on the moon.<p><hr /></p></p></blockquote>Very likely, but the Moon's surface is strewn with secondary projectiles from primary impacts, so looking for a meteorite from Mercury there would be like searching for a needle in a haystack.

 

[earthseed]

The moon also probably contains fragments from the early Earth ejected from large meteor impacts. This could give us information that we cannot get here on Earth because of tectonic recycling - none of the original surface is available anymore. Sure, it is a needle in a haystack, but a good part of science is about finding those needles.

 

[yevaud]

Mass and mass alone. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[steampower]

if you imagine a protostar as a bag full of gas, then the bag can be any size, but once the gravity pulls it together, the pressure rises to ignition point, big lumps of gas squeeze up to make big stars, small lumps make small stars, realy small make no star at all (or a brown dwarf), plus the realy large clumps are accelerating as they fall into their center of gravity for longer than the small ones, for a guess that creates shockwaves that may ****** the collapse or soften it, either way, I think its density, not mass that dictates when they ignite, so two cubic light years of hydrogen or one cubic light year collapsing to their center of gravity, they both need the same pressure, but one will be eight times bigger than the other when it gets to that pressure.<br /><br />steampower.

 

[yevaud]

Beat me to it (been busy). True, although density and mass are inextricably connected. And yes, the dynamics of how the protostar accretes as well. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>