# Mercury, Large quantity water ice

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How do Scientists prove that all the water on Mercury was brought there by comets?

Edited by DarkStar8
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It seems more likely to me that water ice on the surface of the Mercury comes from superheated steam blown on it from the Sun rather than comets. Surely, if all ices were deposited by comets , then all the planetoids surfaces throughout the solar system would not have their water ices deposited so uniformly about their surfaces.

The article you cited later discussed the presence of water in sunspots, not the solar wind. Sunspots are relatively cool regions on the surface of the Sun, cool enough that molecules can form. The solar wind is borne from the Sun's outer atmosphere and has temperatures of nearly a million kelvin, or more. There is no water in the solar wind; it's too hot.

Another problem with this hypothesis is abundance (or lack thereof). Oxygen is but a trace element in the Sun itself; about 0.078% of the atoms in the Sun are oxygen atoms. Oxygen is an even smaller component of the solar wind.

That said, there is a related hypothesis that does posit the solar wind as the source of water on the Moon, and possibly other bodies as well. Oxygen or water is not needed. All that's needed is protons, which along with electrons are the dominant component of the solar wind. Per this hypothesis, the protons in the solar wind interacted with the oxygen already present in a body's surface or atmosphere to form water.

Yang Liu, et al., Direct measurement of hydroxyl in the lunar regolith and the origin of lunar surface, Nature Geoscience 5, 779–782 (2012)

http://www.nature.com/ngeo/journal/v5/n11/full/ngeo1601.html

h

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How do Scientists prove that all the water on Mercury was brought there by comets?

It is not a matter of proof, it is a matter of probabilities.

We know that comets contain substantial amounts of water.

We know that there are many comets.

We know that comets do impact the planets.

We know that a portion of the water will be retained by the planet.

We know that parts of Mercury are not exposed to sunlight.

Now we have found water in such locations.

The reasonable presumption is that the source is comets.

It is reasonable to consider other possibilities. However, there appears to be less evidence for your proposal than the current standard one.

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D H, that sounds a plausible hypothesis.

Edited by DarkStar8
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• 1 month later...

Do you realize how hard it is to get to Mercury? There's a reason NASA (and nobody else) has sent all of two missions to Mercury, while practically every space faring nation has sent multiple missions to Mars. Getting even close to Mercury an extremely expensive endeavor. Placing a vehicle in orbit about Mercury is monstrously expensive. Landing on Mercury would be even more than monstrously expensive.

Short of some huge breakthrough in propulsion technology, we will never send people to Mercury. Never. Even if humanity does develop that requisite breakthrough technology, this will not change the huge cost in getting to Mercury. That cost is always present. It is far cheaper to send machinery and people to practically any other place in the solar system.

Never say never. Given that we now know (since 1985) how to use gravity assists to get to Mercury, a manned mission may not be as impossible as you say. After some searching I found that 590 kg of fuel were used for the Mercury MESSENGER trip. In comparison, the Mars Reconnisance Orbiter used 1149 kg, Mars Express used 370kg and Cassini used about 3000kg. So there doesn't appear to be any big difference from missions to other planets in terms of fuel use or expense, just in the travel time. If there was a good reason for going to Mercury, people could withstand a 6.5 year journey, given suitable provisions. Perhaps the reason would be to start an underground colony near the poles and water deposits. At the right latitude, and a couple meters underground, there would be constant room temperture. And there would be ample sunlight for solar power and agriculture. For a 6.5 year journey, protection from ionizing radiation would probably be the biggest obstacle to overcome.

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Never say never. Given that we now know (since 1985) how to use gravity assists to get to Mercury, a manned mission may not be as impossible as you say. After some searching I found that 590 kg of fuel were used for the Mercury MESSENGER trip. In comparison, the Mars Reconnisance Orbiter used 1149 kg, Mars Express used 370kg and Cassini used about 3000kg. So there doesn't appear to be any big difference from missions to other planets in terms of fuel use or expense, just in the travel time. If there was a good reason for going to Mercury, people could withstand a 6.5 year journey, given suitable provisions. Perhaps the reason would be to start an underground colony near the poles and water deposits. At the right latitude, and a couple meters underground, there would be constant room temperture. And there would be ample sunlight for solar power and agriculture. For a 6.5 year journey, protection from ionizing radiation would probably be the biggest obstacle to overcome.

Not that it counters your argument - but it is crucial to know the mass of the craft as well as the fuel burnt

$\begin{array}{cccc} craft&total&fuel&dry \\ \hline Messenger&1111&600&485 \\ MRO&2180&1149&1031 \\ MarsXpress&1123&457&666 \\ Cas-Huy&5600&2823&2523 \\ \end{array}$

All masses are in kilos - and I realise they do not add up but I had to get info from various sources, but they give a good idea

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• 6 months later...

I would like to re-open this discussion. . .

Reading these posts, I noted two things:

1) There was no discussion of why we would want to send people to Mercury.

2) There was no mention of solar sails, which are a game changer for travel to Mercury.

Mercury has awesome potential as an astronomical observatory. All wavelengths are available to the surface for 88 straight days of observing. Mercury provides most of the materials one would expect to build optical and radio telescopes out of - seriously reducing mass required from Earth/Moon. We are spending 8 billion dollars to build & launch the James Webb Space Telescope alone. when you consider that Kepler, Chandra, and other orbiting telescopes all are approaching the end of their useful lives, the total replacement costs are well into the tens of billions - with no technicians in orbit to ensure the 'scopes keep working or are upgraded periodically. A base on Mercury could do that rather handsomely. Of course there are other reasons for settling Mercury. . .

Solar sails are able to move large masses to Mercury from Earth in reasonable time periods. The late Robert Forward, of JPL, outlined capabilities of 185 metric ton payloads delivered to Mercury orbit in flights of 2.3 years. Manned flights would not need anything near that massive for exploration missions, suggesting they would be faster. Mercury's photon flux is so great that the sail material to be used was a relatively 'heavy' (10 gm/m2) material that was already available in 1980. Contrast that with our maximum payload capability to Mars of about 50 tons every 2.13 years.

I hope to discuss this further. The possibilities for Mercury are simply awesome!

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Seems to me that the problem with Mercury would be getting back, not getting there. And on the dark side one has exposure to deep space radiation, micrometeorites, etc., as with easier reached places such as our moon. Robots, maybe, would be the colonists if any.

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Getting back is the same problem as getting there: having a transportation system that can develop the velocity change needed. The confirmed presence of large quantities of water means we can definitely support either LO2/LH2 or H2 systems on an economical basis. This means we can reasonably contemplate using all-propulsive ballistic transfers. These have flight times averaging 105 days (some flights are only 85 days long) with important implications for a human crew's payload mass.

Mass ratios for Mercury orbit Insertion (MOI) range between 4 and 7.7 for the LO/LH systems.A hydrogen burning Solar Thermal stage would do very much better with mass ratios of 1.75 to 2.3. I base these on Specific Impulse of 465 sec. for LO/LH and 1150 sec, for LH systems.

More generally, neither the Moon or any of the planets are 'easy' to reach. They all require billions of dollars in infrastructure to access and utilize. What matters is what we get in return. With Mercury, at a minimum, you access resources, energy in great quantity and a launch window advantage (compared to Earth's situation) that is unmatched anywhere else. Ditto for Mercury as a science platform.

Energy + Resources + Location + Environment = Potential For Colonization

Mercury provides energy via the Sun, of course, but there is also a still-molten (outer?) core that almost certainly still changes things on parts of Mercury's surface occasionally.

Resources there are typical of asteroids - rather mediocre, to be frank - but the thermal energy surplus makes them economically viable as so far 'ores' are defined.

Mercury's orbit is a good place to launch operations to other planets from. With the exception of Venus, it is possible to launch to other planets at least three times every calendar year. For outer planets it is four times.

Relying on robotics assumes the number and endurance of the robots is sufficient to operate essentially trouble-free as there is no way to fix them (except maybe with other robots). what miught be the cost of a robot to do both mining and telescope building? I have to believe it gets prohibitive. . .

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pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

Large quantities of water ice on Mercury.

This is an interesting news article about finding large quantities of water ice at Mercury's poles, estimated to be between 100 billion and a trillion tons of water. This seems like a good place for future colonization like the moon, and easier than Mars. We could develop underground colonies in locations near the water sources at Mercury's poles as well as at the lunar poles. Both polar locations could transfer nearby heat from the sun for solar heating, to supply electrical energy for such a colony, and lighting for underground farming. Solar or nuclear power could be provided for manufacturing and mining. Based upon these water resources, its closer proximity, and accessible water supply, it may be easier to colonize Mercury than Mars. Much less fuel would be needed to escape its gravity, where hydrogen and oxygen fuel could be readily manufactured on site. The underground colonies might be able to spread out in all directions from the poles including downward, only limited in its extent by temperature control.

Large quantities of ice on Mercury.

pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

Large quantities of water ice on Mercury.

This is an interesting news article about finding large quantities of water ice at Mercury's poles, estimated to be between 100 billion and a trillion tons of water. This seems like a good place for future colonization like the moon, and easier than Mars. We could develop underground colonies in locations near the water sources at Mercury's poles as well as at the lunar poles. Both polar locations could transfer nearby heat from the sun for solar heating, to supply electrical energy for such a colony, and lighting for underground farming. Solar or nuclear power could be provided for manufacturing and mining. Based upon these water resources, its closer proximity, and accessible water supply, it may be easier to colonize Mercury than Mars. Much less fuel would be needed to escape its gravity, where hydrogen and oxygen fuel could be readily manufactured on site. The underground colonies might be able to spread out in all directions from the poles including downward, only limited in its extent by temperature control.

Large quantities of ice on Mercury.

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The ice is not exposed. v vIt seems to be either covered by or misxed with a regolkith component containing hydroca4rbon material. This suggests it is cometary in nature as such minerals are freq

uently found in comets. We do not yet know, exactly, the chemical make-up of the material, but the insulating properties are likely to be at least as good as the regolith found elsewhere on Mercury.

Sorry for the typos. . .

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You are missing the point. It takes a great amount of fuel to escape a gravity well such as near a black hole, whereby it takes none to get "pulled in" by gravity, less fuel to go to Mercury than to leave it going back. This is not Sci Fi.

We don't have to get stationary relative to the sun. By going opposite the rotation of the Earth the sun's gravity helps pull you toward your destination. 30km/sec is 108,000 Km per hour. We have no problem achieving half that speed. The point is that the pull of the sun's gravity can assist a craft inward toward the sun.

I agree with your point that presently there is little point to sending nuclear waste inward toward the sun. But with nuclear rockets, or better, less expensive propulsion systems, I expect it will happen someday.

OK

We may be on the same page here but I think the technology of nuclear powered spacecraft is already here. It just needs the political will to do it, and the time to perfect and debug such a system. I also expect positron rocket propulsion is maybe only 50 years away, even though we haven't even started on it in earnest as yet.

I think we will see serious proposals for man to go to Mercury within the next century. I also think there will be one or more mining colonies there within the next few centuries.

//

Actually, we see 'serious proposals' to go to Mercury now. The only problem is they come from the space settlement advocacy and not NASA itself or its industrial support. That is why I'm here. There is polite tolerance in some industry circles for going to Mercury, but it is premature to commit to the idea before we resolve important issues - such as the radiation effects on people who go there. This site offers a real shot at getting these issues addressed by people who actually know how to work them. Sadly, I'm only a journalist.

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Actually, we see 'serious proposals' to go to Mercury now. The only problem is they come from the space settlement advocacy and not NASA itself or its industrial support.

Actually, we don't see any 'serious proposals' to go to Mercury for the sort of operations you are proposing. The space settlement advocacy is the quintessential source of non-serious proposals of all sort. Space settlement on an extremely small scale, on close-by objects *might* happen in the next few decades. Space settlement on the scale advocated by those advocacy groups: It ain't gonna happen, not in my lifetime, probably not in yours.

You have predicated your Mercury proposal on a large number of technologies that we don't know how to do from an economic or engineering perspective. Space mining? We don't know how to do that. Space manufacturing? We don't know how to do that, either. The same applies to large solar sails, solar thermal propulsion, getting people to and from Mercury. We don't know how to do any of them. All of these are at a very low technology readiness level. TRL 4 is where we can start saying we know how to do that. None of these is even close.

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Actually, we don't see any 'serious proposals' to go to Mercury for the sort of operations you are proposing. The space settlement advocacy is the quintessential source of non-serious proposals of all sort. Space settlement on an extremely small scale, on close-by objects *might* happen in the next few decades. Space settlement on the scale advocated by those advocacy groups: It ain't gonna happen, not in my lifetime, probably not in yours.

You have predicated your Mercury proposal on a large number of technologies that we don't know how to do from an economic or engineering perspective. Space mining? We don't know how to do that. Space manufacturing? We don't know how to do that, either. The same applies to large solar sails, solar thermal propulsion, getting people to and from Mercury. We don't know how to do any of them. All of these are at a very low technology readiness level. TRL 4 is where we can start saying we know how to do that. None of these is even close.

I agree with your assessment of space advocacy groups being the source of non-serious proposals. The Mercury study is all about determining how - not if - we could mine Mercury on an economical basis. The Japanese flew their IKAROS solar sail to Venus successfully. It operated for months under their control and performed as expected.

We have been operating large cryogenic propulsion stages in space for decades. That is all a Solar Thermal Rocket is and it is based on known technologies from Nerva and Apollo operations. It is not just theoretical conjuring.

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I have predicated my proposal on the idea that energy is key to doing anything in space. The more you have of it, the better off you are. Carefully note that I started by talking about astronomy. Not always the first choice for most space advocates. We are already doing astronomy. Mercury is just a better (more cost-efficient) location for it. I didn't talk about Helium-3. Now that is a technology that is way off practically and economically.

At this point I have seriously strayed from the original subject of this post and that is a no-no. I apologize to the poster. . . Perhaps I/we should post in a different forum?

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pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

!

Moderator Note

Arguments concerning the age of the planets or solar system are not the topic of this discussion.

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pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

pantheory, hi creationist here. one thing that is interesting about finding exposed water ice on mercury is that even at temperatures close to zero kelvin,sublimation is still an important factor. this calles into question the age of this water,presumably also,the age of mercury. the finding strongly suggests that the ice cannot be millions of years old. by itself,of course, this is a weak argument for a young solar system; however this and other factors begain adding up to a strong argument.

So creationist, i guess you didn't read the link in the OP?

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Very interesting. When I had read about the possbility awhile back, I thought it was a bit strange. With very little atmosphere, I would have thought that the ice would sublimate in short order. But I guess at those low temps, it may not happen.

So it might be a more ideal first colony when compared to Mars in some ways. But, I think there is still the issue of radiation. The interior of the planet would be protective, but a ship would need to get there, and would be exposed.

The asteroid 24 Themis has similar thermal conditions to Mercury's poles. Water ice has been discovered on it's surface which was surprising as the sublimation rate that far from the Sun (~3.5 AU) would suggest the surface should be devoid of ices. It was suggested the water came from Themis' interior, but Themis is about 200 km diameter and would not likely have a warm enough core to support volcanic heating of subsurface water. Mercury is actively volcanic in its core, however. We may be seeing the surface manifestation of subsurface water being driven to the surface in aeons past.

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You are missing the point. It takes a great amount of fuel to escape a gravity well such as near a black hole, whereby it takes none to get "pulled in" by gravity, less fuel to go to Mercury than to leave it going back. This is not Sci Fi.

We don't have to get stationary relative to the sun. By going opposite the rotation of the Earth the sun's gravity helps pull you toward your destination. 30km/sec is 108,000 Km per hour. We have no problem achieving half that speed. The point is that the pull of the sun's gravity can assist a craft inward toward the sun.

Look, in order to get to Mercury you have to shed a fair portion of the Earth's orbital speed. Just firing your engines in a direction opposing the Earth's orbital direction isn't going to do it unless you make a large enough change in ytour speed. Anything less just puts you in an eliptical orbit which has a perihelion further from the Sun than Mercury is. In order to get your trajectory to intersect with Mercury's orbit you have to get your orbital speed at Earth orbit distance down to, at most, 22 km/s, which means you have to change your velocity by ~8 km/sec.

As you fall in towards the Sun you will pick up speed and by the time you reach Mercury's orbit, you will be moving at 57 km/sec.

Mercury's orbital speed is 48 km/s. So in order to safely rendevous with it ( and not just slam into it at high speed) you are going to have to shed 9 km/sec. This puts the total velocity change needed 17 km/sec. And this doesn't even take into account what it would take to lower yourself to the surface.

In order to leave the solar system completely from Earth orbit requries a velocity change of only 12.4 km/sec.

As to what a 17 km/sec velocity change means in terms of fuel:

If we assume a exhaust velocity of 4500 m/s (about as good as you'll get with a chemical rocket), it works out that you'll need ~43 kg of fuel for every kg of payload you want to get to Mercury.

If you want to land, this jumps up to 116. If you want to include a return trip, you are now talking 13750 kg of fuel for every kg that you land on Mercury and return to Earth orbit.

Basically, the ratio of fuel to payload varies by the power of the total speed change divided by the exhaust speed of your rocket. If the velocity change doubles, the mass ratio increases by a power of 2.

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Look, in order to get to Mercury you have to shed a fair portion of the Earth's orbital speed. Just firing your engines in a direction opposing the Earth's orbital direction isn't going to do it unless you make a large enough change in ytour speed. Anything less just puts you in an eliptical orbit which has a perihelion further from the Sun than Mercury is. In order to get your trajectory to intersect with Mercury's orbit you have to get your orbital speed at Earth orbit distance down to, at most, 22 km/s, which means you have to change your velocity by ~8 km/sec.

As you fall in towards the Sun you will pick up speed and by the time you reach Mercury's orbit, you will be moving at 57 km/sec.

Mercury's orbital speed is 48 km/s. So in order to safely rendevous with it ( and not just slam into it at high speed) you are going to have to shed 9 km/sec. This puts the total velocity change needed 17 km/sec. And this doesn't even take into account what it would take to lower yourself to the surface.

In order to leave the solar system completely from Earth orbit requries a velocity change of only 12.4 km/sec.

As to what a 17 km/sec velocity change means in terms of fuel:

If we assume a exhaust velocity of 4500 m/s (about as good as you'll get with a chemical rocket), it works out that you'll need ~43 kg of fuel for every kg of payload you want to get to Mercury.

If you want to land, this jumps up to 116. If you want to include a return trip, you are now talking 13750 kg of fuel for every kg that you land on Mercury and return to Earth orbit.

Basically, the ratio of fuel to payload varies by the power of the total speed change divided by the exhaust speed of your rocket. If the velocity change doubles, the mass ratio increases by a power of 2.

All very accurate. But what exactly is your point? Are you trying to say it is too expensive in delta-v terms? If this were being done for a manned mission, the propellant requirements would be two to three times that required for a similar mission to Mars. Sounds bad, but the manned payload for Mercury would have a much lower mass because the total mission time is about 440 days, as compared to the ~900 days for the Mars mission. Less consumables have to be carried. Less spacecraft volume is needed to accommodate the remaining consumables while still holding to NASA's criteria for crew volume. Less volume equals smaller, lighter payload mass. All together, propellant mass for the Mercury mission would actually be about 1.2 to 1.5 times that needed for a Mars mission. Not the 2 or 3 times indicated by delta-V figures alone.

You were right about the exhaust velocity of 4500 m/sec. the J2X was intended to operate with Specific Impulse of 465 sec. (optimistic, IMHO) yielding exhaust velocity of 4561 m/sec. That is why we went with the Solar Thermal Rocket for manned missions only. Different sources gave a variety of figures for Isp starting at 980 and going up to 1300.sec. 1150 sec. seems conservative. This is very sustainable from Mercury's resources.

Supplying propellant in Mercury orbit enables the mission to be broken down into two distinct legs. This is nothing different than what is being contemplated for Mars missions. The ability to actually produce rocket propellant on Mercury itself makes the horrendous 'all-up' mass figure you noted (13750 kg/kg spacecraft) unnecessary.

This is why the matter needs in-depth study. Mercury is not Mars and flights to Mercury are not the same as flights to Mars. The spacecraft won't be the same either, if we are wise.

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All very accurate. But what exactly is your point? Are you trying to say it is too expensive in delta-v terms?

That is his point.

If this were being done for a manned mission, the propellant requirements would be two to three times that required for a similar mission to Mars.

Nonsense. There is no point other than scientific curiosity in going to Mercury. There is no point at all in sending humans there, at least not in our lifetime.

Getting to Mars is cheap. The delta V requirements for a one-way mission to Mars is less than a third, and maybe less than a quarter, of that for a one-way mission to Mercury. A round-trip mission to the surface Mars and back to Earth, while costly, is cheaper yet compared to a round-trip mission to the surface of Mercury and back to Earth.

To make matters worse, that factor of 3 or 4 or more in delta V translates into a huge factor in terms of fuel. The amount of fuel needed is not a linear function of delta V. Fuel costs grow exponentially as delta V increases.

Any resources on Mercury are much more easily obtained in the asteroids. Or for that matter, right here on Earth. The idea of mining asteroids (or the Moon, or Mercury) and sending the mined items back to Earth is, for now, science fantasy. The first materials that will be mined in space are things that are very easily obtained: water and other volatiles. There is no value in sending these materials back to Earth. Common metals mined in space such as iron and nickel will have zero value back on Earth. They're too common. Only the very rarest of materials might have value on Earth, but mining those falls into the category of "we haven't the foggiest idea how to do that."

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That is his point.

Nonsense. There is no point other than scientific curiosity in going to Mercury. There is no point at all in sending humans there, at least not in our lifetime.

Getting to Mars is cheap. The delta V requirements for a one-way mission to Mars is less than a third, and maybe less than a quarter, of that for a one-way mission to Mercury. A round-trip mission to the surface Mars and back to Earth, while costly, is cheaper yet compared to a round-trip mission to the surface of Mercury and back to Earth.

To make matters worse, that factor of 3 or 4 or more in delta V translates into a huge factor in terms of fuel. The amount of fuel needed is not a linear function of delta V. Fuel costs grow exponentially as delta V increases.

Any resources on Mercury are much more easily obtained in the asteroids. Or for that matter, right here on Earth. The idea of mining asteroids (or the Moon, or Mercury) and sending the mined items back to Earth is, for now, science fantasy. The first materials that will be mined in space are things that are very easily obtained: water and other volatiles. There is no value in sending these materials back to Earth. Common metals mined in space such as iron and nickel will have zero value back on Earth. They're too common. Only the very rarest of materials might have value on Earth, but mining those falls into the category of "we haven't the foggiest idea how to do that."

Payload masses are what determines how much propellant you need. Delta-V only determines how much propellant you need per unit mass of payload.

Getting to Mars is cheaper. My own figures say that. What I was saying is that a mission to Mercury is possible for propellant loads that are within the same mass range we are already planning for Mars.

Mercury is a multi-functional place where science ( mostly astronomy, solar physics and planetary science) and industry are uniquely facilitated - due mainly to solar sail's impact on transportation costs, the super-abundance of energy on site and the seven-fold grater frequency of launch opportunities for a given transport system..

Carefully note that I am not suggesting Mercury as an alternative to Mars, but as a synergistic relationship WITH Mars.

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• 2 weeks later...

The interesting possibility would be that if there is enough water on Mercury, and if by robotic exploration we would find out how much and accurately where water exists, a manned spacecraft could someday convert solar radiation into electricity that could dissasociate water into oxygen and hydrogen, a great rocket fuel for a return trip. This technique might also be used for a round trip to Mars and the moons of Jupiter, to get a spacecraft back, using either solar energy or atomic energy for the electricity needed to dissasociate water and create fuel. And of course water would be needed in the more distant future for the underground human colonization of Mercury near its polar regions, which also seeminly would be feasible to learn first on our moon.

Of course water could also be manufactured on the moon, Mars, and Mercury from materials found near the surface, if there is otherwise a sparcity of water at a particular location, or if transportation of water at that location might be more costly to find and/or transport.

Edited by pantheory
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The interesting possibility would be that if there is enough water on Mercury, and if by robotic exploration we would find out how much and accurately where water exists, a manned spacecraft could someday convert solar radiation into electricity that could dissasociate water into oxygen and hydrogen, a great rocket fuel for a return trip. This technique might also be used for a round trip to Mars and the moons of Jupiter, to get a spacecraft back, using either solar energy or atomic energy for the electricity needed to dissasociate water and create fuel. And of course water would be needed in the more distant future for the underground human colonization of Mercury near its polar regions, which also seeminly would be feasible to learn first on our moon.

Of course water could also be manufactured on the moon, Mars, and Mercury from materials found near the surface, if there is otherwise a sparcity of water at a particular location, or if transportation of water at that location might be more costly to find and/or transport.

The most recent estimates put Mercury's water supply into the trillions of tons. Developing Mercury's resources would be more about using them to make finished products than just exporting raw ores back to Earth or Mars. Mars has all the same resources Mercury has. What it does not have is the energy supply Mercury has. Particularly where solar heat is concerned. Mercury has twenty times the solar flux of Mars. That makes it cheaper to produce tons of whatever you care to fabricate. The fact that Mercury can send materials to Mars seven times more frequently than Earth is also a point in Mercury's favor. Individual sails are inherently more efficient when flown from Mercury than Earth - they carry more payload for a given sail area and accelerate at a faster rate than Earth-launched counterparts. Overall, transporting a mass from Mercury to Mars is cheaper than transporting the same mass from Earth.

What I see evolving from this is a scenario where Mars and Mercury are developed more or less simultaneously. Mercury is given the tools to develop construction materials for Mars. Mars colonization would proceed at a greater pace as Earth's transportation system would be utilized more efficiently by not having to send so much deadweight

As for asteroids. . . The delta-V advantage they have does not quite cancel the fact they are interplanetary missions with infrequent launch windows. The more their orbits resemble the Earth's, the more they share of Earth's launch window disadvantage for interplanetary missions. .

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