<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>...I thinls Mercury's high mass & density for an object of that size is due to Mercury forming on the inner edge of the protoplanetary disk. I do not think Mercury is an exposed anything.Perhaps MESSENGER may show something to refute that, but I do not think so. Andrew Brown. <br />Posted by 3488</DIV><br /><br />Hello Andrew,</p><p>If you recall, there are several journal papers which have expounded on the hypothesis that Mercury is a stripped core, caused by a mega collision early in its history. One of the first of these is below. I think it is interesting that Mercury and earth both might have had similar early histories, both planets believed to have been smacked by a protoplanet (which formed earth's moon).</p><div id="artihead" class="artihead">
<strong>Icarus</strong><br />
Volume 74, Issue 3, June 1988, Pages 516-528 </div><div class="articleTitle"><p><strong><font size="5">Collisional stripping of Mercury's mantle</font></strong> </p><div class="refMsg nojs" style="display:none"><br /><br /> </div></div><div id="authorsAnchors" class="authorsNoEnt"><strong><p>Willy Benz
<sup>*</sup>, Wayne L. Slattery
<sup>†</sup> and A. G. W. Cameron
<sup>*</sup></p></strong></div><div class="articleText" style="display:inline"><div id="authorsAnchors" class="authorsNoEnt"><p><a name="aff1"></a><sup>*</sup> Harvard-Smithsonian Center for Astrophysics, Harvard College Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, USA</p><p><a name="aff2"></a><sup>†</sup> Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA</p></div></div><div class="articleText" style="display:inline"><br />Received 19 June 1987; </div><div class="articleText" style="display:inline">revised 7 October 1987. </div><div class="articleText" style="display:inline">Available online 26 October 2002. </div><br /><div class="articleText" style="display:inline"><h3 class="h3">Abstract</h3><p>We investigated the conditions under which a giant collision between a hypothetical proto-Mercury and a planet one-sixth its mass would result in the loss of most of the silicate mantle of the planet, leaving behind an iron-rich planet and thus explaining the anomalously high density of Mercury. We carried out a series of numerical simulations using our three-dimensional smoothed particle hydrocode, varying the impact parameter and the relative velocity between the planet and impactor. We demonstrate that the details of the equation of state do not play an important role. We show that a head-on collision at 20 km/sec and an off-axis (impact parameter equal to half the radius of proto-Mercury) collision at 35 km/sec are about equivalent as far as damage to proto-Mercury is concerned. Both collisions leave behind a remnant that has the required characteristics of the present Mercury. Whether this scenario is actually successful depends on the size of the condensates in the ejected cloud of debris. Preliminary estimates show that most of the ejected mass is probably removed from Mercury-crossing orbits. If this turns out to be true, a giant collision is a plausible explanation for the strange density of Mercury.</p><p> </p><p>++++++++++++++++</p><p> Also there are some papers which state that the splashed pieces of Mercury could have ended up all over the inner solar system, some of which hit earth.</p><p>
http://www.astronomy.com/asy/default.aspx?c=a&id=4108</p><div class="articleHeadline"><strong><font size="5">Mercury blast splashed Earth</font></strong></div><div id="ctl00_ContentPlaceHolder_ctl00_divByline"><strong><font size="4">Computer models suggest a giant impact shattered Mercury and showered Earth and Venus with debris</font></strong></div><div>
<img class="imgBorder" src="http://www.astronomy.com/asy/image.ashx?img=mercury_impact.jpg&w=250" alt="Mercury impact simulation" /></div><div><span class="caption">These panels illustrate how a giant impact could have depleted Mercury’s silicate crust and mantle (blue) while leaving behind an oversize iron core (red). Left: An object half Mercury’s present mass collides obliquely with a 2.25-Mercury-mass protoplanet. This view shows the model 2 minutes after the impact. Center: Within 8 minutes of the collision, both worlds are shattered. Right: This wider view shows the scene 3 hours later. Much of the rocky material has been removed and little of it will return. <em>Jonathan Horner, University of Bern</em> [
View Larger Image]</span></div><div></div><div><span class="caption"><span class="news-date">April 5, 2006</span> <br /><span class="dropcap">N</span>ew computer simulations of a giant impact on the young planet Mercury shed light on the planet's odd makeup. Moreover, say scientists, debris from this cosmic collision could have made its way to Earth and Venus.<br /><br />"Mercury is an unusually dense planet, which suggests that it contains far<br />more metal than would be expected for a planet of its size," says Jonathan Horner at the University of Bern, Switzerland. While Earth ranks as the solar system's densest planet, Mercury comes in a close second despite containing just 5.5 percent of Earth's mass. Results from the Mariner 10 spacecraft, which flew past the planet 3 times in the mid-1970s, explained why: Mercury possesses an iron core nearly as large as the planet itself. <br /><br />Scientists had long suspected this supersize core arose early in Mercury's history through a catastrophic collision that blasted away most of the planet's rocky crust and mantle. But, says Horner, "Until these simulations, we were not sure why so little of the planet's outer layers were reaccreted following the impact." <br /><br />Horner and his colleagues Augustin Anic, James Whitby, and Willy Benz simulated collisions between a proto-Mercury 2.25 times the planet's current mass and an impactor half of Mercury's present mass moving at 62,600 mph (100,000 km/h). The result was a dense, metal-rich body and a swath of escaping debris. "The simulations … are very promising," Horner tells <em>Astronomy</em>. "They seem to create an object very much like the Mercury we see, which is obviously a good sign for the theory." He presented the study at the Royal Astronomical Society's National Astronomy Meeting April 4.<br /><br />To follow what happened to the ejected matter, the team fed information about the debris trajectories into a second set of simulations to see how long particles drifted in space before the newly formed Mercury swept them up. The simulation tracked particles until they either landed on a planet, fell into the Sun, or traveled beyond Jupiter. <br /><br />The scientists found that half of the ejecta could take as long as 4 million years to fall back to the planet. That's sufficient time for non-gravitational forces not included in the model — such as radiation pressure from sunlight or the
Poynting-Robertson effect — to alter particle orbits. Most debris in the scientists' impact scenario would never return to Mercury. <br /><br />Interestingly, some of the debris could have reached Venus and even Earth. "It really demonstrates how material spreads out after such an event," Horner says. He thinks Earth may contain as much as 17 million billion tons (16 million billion metric tons) of proto-Mercury. <br /><br />NASA's Messenger spacecraft, now en route, will be the first spacecraft to visit Mercury since Mariner 10. Messenger is scheduled to fly within 124 miles (200 kilometers) of Mercury's surface in January and October 2008 and September 2009. The probe will enter into Mercury orbit in March 2011. <br /><br />View the movie to see a simulated Mercury impact from the University of Bern group. </span></div></div> <div class="Discussion_UserSignature"> <p align="center"><font size="1">petet = <font color="#800000"><strong>silylene</strong></font></font></p><p align="center"><font size="1">Please, please give me my handle back !</font></p> </div>
A video made by me about space and the loneliness in the universe
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