Is there mercury on Mercury? Options

[Guest_Enceladus75_*]

This may sound like a completely stupid and whimsical question, or else give the UMSF food for thought. But does anyone know if there has been any work done on estimating the abundances of metals on Mercury, and with this in mind, in particular I'm wondering if planet Mercury's namesake element, the liquid metal mercury, could exist as an ore in the crust of Mercury?

I guess this speculation is pretty fanciful, but could it be possible for Mercury to contain its namesake metal?

And leading on from that, could Mercury, Mars or Venus contain precious metals such as silver, gold or platinum worth mining in commercial quantities eventually? Or can such metals only be created in sufficient concentrations on Earth only, due to its plate tectonics?

[elakdawalla]

Mercury likely exists in Mercury, as it does in everything else in the solar system, from the Sun to planets, moons, and asteroids. The question is whether we'd be likely to encounter it in any abundance locally. I don't know the answer to that question, but I can send you to a story and a couple of definitions that might be useful in trying to figure it out.

Here's the story: when the terrestrial planets initially formed, they were molten, and separated into iron, nickel, and sulfur-rich cores and rocky mantles, a process called differentiation. One thing that happened during differentiation is that less abundant elements got partitioned into the core and mantle. You might think the heaviest elements would have wound up in the core and the lighter ones in the mantle, but it's not quite that simple. What happened is that elements that have a chemical affinity for iron or sulfur wound up in the core, and the stuff that doesn't, didn't. This is one reason the mantle and crust of Earth is relatively rich in radioactive elements, because those huge atoms don't fit into the chemical lattices that iron-bearing minerals form (unlike, say, magnesium and titanium, which fit quite nicely).

Elements that like iron are called siderophile. Elements that prefer to bond with oxygen, and thus tend to get partitioned into rocky mantle and not core, are called lithophile. While looking this up, I found a third class I hadn't read about before, chalcophile, which like to bond with sulfur so are more likely to end up in the core than the mantle, though they are not as strongly partitioned as siderophile elements. Mercury, along with copper, silver, zinc, arsenic, and lead, are all chalcophile.

Here's a link.

Instinct tells me that Earth would have richer deposits of ores than most other planets, for two reasons. First, the fact that it's had volcanic activity right up to the present means that its rocks have been repeatedly processed -- partially melted, extruded, lithified, then all over again -- which has the potential to concentrate relatively rare elements. Second, it's my understanding (though I'll admit I never took a class in economic geology) that the best way to concentrate ores is to take a relatively enriched source rock and run hot, acidic groundwater through it, dissolving minerals and redepositing them in veins in the rock, which happens in volcanic environments on Earth, but not on, say, Venus, which is pretty much dried out.

--Emily

[Guest_Enceladus75_*]

Emily...that's great food for thought. I'm afraid my detailed geology knowledge only goes to 2nd year university level, and my chemistry to just first year college (I'm a "major" in Geography). But I do try to keep up on reading on the subject of planetary geology and the evolution of the planets in a geochemical context. I'm fascinated by planetary geology, and I was just thinking this evening about the possibility of commercially available ores on other terrestrial bodies in the solar system. I've suspected that Mars may harbour a substantial amount of iron ore, but maybe that's just wishful thinking given the highly oxidised iron rich surface of the planet which we've known since the Viking missions of the mid 1970s. Time will tell.

Of course, at Mercury's temperature, mercury the element would likely be vapourised, but cinnebar, the mercury bearing ore, could potentially be found in its crust. I would agree with your belief that Earth probably is the best location for purer ores, given its dynamic geology, plate tectonics and atmospheric action, but I suspect that Venus is still almost certainly geologically active, and the Magellan mission detected probable concentrations of metals on its higest mountain peaks, like possibly tellurium, so I suppose we won't know for sure until we do a more thorough exploration. And although mercury the element may be a sulphur loving element, we know it didn't all go into Earth's mantle and core as evidenced by its relative abundance in the upper crust.

I just think that it would be sort of cool and ironic if mercury was detected on its namesake planet, Mercury.

Why do the popular science books go on and on about the potential of the asteroids as a future source of important metals all the time? Surely, given their small size and relatively undifferenitated nature, they wouldn't be all that much of a souce of metals more likely found in greater abundance on the terrestrial planets?

[Marz]

Full quote of previous (long) post removed. - Mod

I think there are two reasons asteroids are cited as the 'low-hanging fruit' for mining:
1. the iron-nickel (M-class) are almost pure metal.
2. no gravity well; which means transferring the ore is about as easy as space-freight could get

There are two other classes of 'roids: Stony and Carbonaceous-chondrites, but both are considerably less dense than the M-class. Note that at least 1 'roid, Ceres, is almost certainly differentiated. Vesta might be as well, or perhaps a fragment from a body that once was.

Venus does have active volcanism, but as Emily pointed out, lacks water. It is thought that water acts as the Prime Mover for plate tectonics, so without it, hot spots in the crust are fixed in place. I also don't know much about how metal ores form, but Mercury is the most dense planet out there and likely had (has?) volcanism. I'd imagine it's very rich in iron and other heavier metals. Cinnabar is mercury-sulphide, and sulphides are common in volcanic deposits. So I'd think Mercury, Venus, and perhaps Io would show traces of it.

[Guest_Enceladus75_*]

It's interesting that you mention Venus. I think that there'd be an almost certainty that volanism is still going on. We just haven't seen it yet. The Messenger mission scientists announced earlier this year that they spotted unmistakable volcanic features on the edge of the Caloris Basin of Mercury, so we do know that Mercury was volcanic in its past. I have a hunch that Mars probably contains commercially minable quantities of iron and iron loving metals, but we just don't know for certain yet.

It's also interesting that you mention Io, yes Io could conceivably be a source of many heavy/precious metals, but the problem in accessing a pretty much molten suface would be difficult.

But what about precious metals, like gold, silver, platinum and rhodium? Would these be available in extractable quantities on the other terrestrial planets, like Venus and Mars?

[silylene]

Mercury likely exists in Mercury, as it does in everything else in the solar system, from the Sun to planets, moons, and asteroids. The question is whether we'd be likely to encounter it in any abundance locally. I don't know the answer to that question, but I can send you to a story and a couple of definitions that might be useful in trying to figure it out.

Here's the story: when the terrestrial planets initially formed, they were molten, and separated into iron, nickel, and sulfur-rich cores and rocky mantles, a process called differentiation. One thing that happened during differentiation is that less abundant elements got partitioned into the core and mantle. .........

--Emily

I was thinking that maybe there is a mechanism that some tiny amounts of elemental Hg could actually coincentrated enough to be found on Mercury. I agree with you that there would expected to be only very trace amounts of Hg in the planet's crust, originally present in oxidized states. But what little there is perhaps could slowly vaporize if the mercury contaning minerals decompose under the intense heat / light, and move in the gaseous form into cooler regions. Gaseous mercury would then recondense in the cold, permanently shadowed polar craters. Once there, it would be permanent. So maybe tiny traces of Hg could be found in those locations via this concentration mechanism.

(Perhaps via similar mechanisms, tiny traces of mercury could be found in the moon's permanently shadowed craters too.)

[djellison]

maybe tiny traces of Hg could be found in those locations via this concentration mechanism.

Could the same not be true of any heavy element? How would this mechanism favour Hg over anything else?

[silylene]

Could the same not be true of any heavy element? How would this mechanism favour Hg over anything else?

It would need to be an element with a substantial vapor pressure when heated, and a element which is easily released from its oxidized state by high heat, or high irradiation. Mercury is particularly well suited in this respect. I could imagine a few other metallic elements which may also collect in the polar regions via this mechanism (especially Na, K, Cs, Rb and Ga). I need to look up the elemental volatilities, and Td's of their oxides and sulfides before responding further.

I always wondered if the probes looking at the polar regions of the Moon or Mercury had the capability to look for the gaseous signature any of the heavier metals.

[dburt]

I have long taught courses dealing with terrestrial ore deposits, have explored for them as recently as last summer (in Mexico), and have also published on lunar and martian mining, so perhaps I should contribute. What has been said so far is fine as far as it goes, but is incomplete.

Regarding mercury, it is the only familiar metal that is liquid at room temperature. Although chalcophile (sulfur-loving), it is only very weakly so - you can smelt it from cinnibar (the sulfide) in a candle flame. Note: You can even smelt lead from its sulfide, galena, in a candle flame, if you supply extra oxygen through a tube called a blowpipe. Because both mercury and lead are poisons, as is the sulfur dioxide produced, I don't recommend trying this experiment with a candle at home. Mercury metal also boils easily, and historically used to be recovered (separated from cinnibar or gold) in a retort (a still for metals). "Dreamy Draw" in Phoenix allegedly gets its name from the weird behaviour of local mercury miners who had been poisoned by the vapors from these retorts.

In light of the above, silyene's suggestion of looking for concentrations of metallic mercury in cold traps on the hot planet Mercury is an entirely reasonable one. Such cold traps probably don't exist on Venus, which is too hot everywhere. Small mercury deposits on Earth are largely found in hot spring or volcanic areas, where hot, sulfurous vapors and liquids have deposited cinnibar or the metal as they approach the cold surface. It has been suggested that somewhat similar small deposits of fumarolic salts or metals might occur in volcanic areas of the Moon or Mars.

Although certain alkali metals (Na, K, Cs, and Rb) have relatively high vapor pressures, they are strongly lithophile (oxygen-loving) and in nature are strongly combined with oxygen in silicate minerals such as feldspars, and therefore are not free to boil off. They will boil off in a vacuum at extremely high temperatures, above the melting temperature of the silicate rock, and therefore lunar rocks are somewhat depleted in them, I understand (presumably from the magma ocean stage, and later the bombardment stage).

To make an ore deposit of a metal, you need, in general, to dissolve it in some fluid, transport it to a new place, and deposit it as a concentration far greater than that in a normal rock. Some partial exceptions: 1) For a placer deposit, as of gold, the fluid (liquid water) merely transports and concentrates the metal, without dissolving it. 2) For a different type of placer deposit, such as the hematitic spherules at Meridiani on Mars, the wind transports sand grains away, leaving the larger, denser spherules as a lag deposit. Gold nuggets can be similarly concentrated as a lag deposit. 3) For bauxite (aluminum ore), the fluid (warm acid rainwater) leaches all other metals, leaving a concentration of insoluble aluminum behind as a lateritic soil in the jungle.

The mercury vapor cold trap discussed above is one example of fluid dissolution, transport, and deposition - here the fluid is a gas (vapor). A silicate melt (molten magma) is another type of fluid that will serve, and its crystallization can concentrate metals such as iron, titanium, chromium, vanadium, nickel, and platinum-group elements. Such magmatic concentrations of metals could occur on any terrestrial planet, or the Moon. For most familar ore deposit types on Earth, the fluid involved is liquid water, steam, or a high pressure supercritical fluid with properties intermediate between those water and steam. To discuss the entire variety of aqueously-produced ore deposits would take far too much space; buy a book. Suffice it to say that plate tectonics, oceans, and precipitation are key to producing major deposits, and the only other terrestrial planet with rather weak possibilities for such deposits appears to be Mars.

Ore is defined as a rock that can be sold for a profit (i.e., for more money than it costs to obtain it). By that definition, without a ready market at hand for its product, there can be no ore deposit. Therefore, until people are actually living and working in space and need locally-derived metals, to speak of metallic ore deposits on Mercury, Mars, or the Moon is probably an oxymoron (inherent contradiction). It has been suggested that certain high-value products of the lunar surface (e.g., helium-3 for future fusion reactors, or platinum-group elements in lavas or from meteorites) or of metallic asteroids (containing dissolved platinum-group elements) might be worth bringing back to Earth for marketing, but so far no one is investing serious money in that idea.

--HDP Don

[Guest_Enceladus75_*]

Many thanks for your contribution dburt - it's great to get an expert opinion. So basically, it IS possible that there could be deposits of mercury the element inside Mercury the planet's polar craters. That's fascinating.

When humans come to colonise and settle on other planets (Mars being the most likely in the forseeable future) they will need to mine metals and other minerals from local resources, so a debate about mineral and metallic depisits on other planets seems to be an important discussion.

[silylene]

I was thinking that maybe there is a mechanism that some tiny amounts of elemental Hg could actually coincentrated enough to be found on Mercury. I agree with you that there would expected to be only very trace amounts of Hg in the planet's crust, originally present in oxidized states. But what little there is perhaps could slowly vaporize if the mercury contaning minerals decompose under the intense heat / light, and move in the gaseous form into cooler regions. Gaseous mercury would then recondense in the cold, permanently shadowed polar craters. Once there, it would be permanent. So maybe tiny traces of Hg could be found in those locations via this concentration mechanism.

(Perhaps via similar mechanisms, tiny traces of mercury could be found in the moon's permanently shadowed craters too.)

Interestingly, Hg was recently discovered on the moon in permanently dark craters via this mechanism . I guess the chances of finding Hg in permanently dark craters on Mercury are now much more likely.

http://www.space.com/scienceastronomy/how-...oon-101021.html

LAMP detected molecular hydrogen, carbon monoxide, calcium, magnesium — and, oddly, mercury.

"When one of our team suggested it was mercury when we were just throwing out ideas, well, I said, 'What a stupid idea, how can there be mercury there,'" Gladstone recalled. "I had to eat my words later."

The rock samples the Apollo missions brought to Earth showed heavier levels of mercury deeper down, which led one retired scientist, George Reed, to propose that sunlight might have baked the mercury out from the soil that then got trapped in craters at the south pole.

"He did a simple back-of-the-envelope calculation and nailed it," Gladstone told SPACE.com. "If I made a great prediction like that, I'd be tickled that I was right."

"The detection of mercury in the soil was the biggest surprise, especially that it's in about the same abundance as the water detected by LCROSS," said LAMP team member Kurt Retherford at the Southwest Research Institute. "Its toxicity could present a challenge for human exploration."

These findings support the idea that the freezing cold of the permanently shadowed regions of the moon can trap vaporized compounds that wafted in from deep space or other areas of the moon and preserved them there for eons. "They're almost literally gold mines for science," Gladstone said.