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NASA's New Horizons Shows Pluto's Moon Charon Is a Strange, New World
MarkWhittington writes: NASA's New Horizons has returned a stunning series of images of Pluto, the dwarf planet that resides on the edge of the solar system, revealing a strange new world of ice mountains and glaciers of frozen nitrogen. NASA also released images of Pluto's largest moon Charon. Scientists expected a plain ball of rock pockmarked with craters, but what they saw was anything but plain and monotonous.
We can, when you're willing to call Vesta, Ceres, Haumea, Makemake, Eris, Sedna, Sila-Nunam, Varuna, Quaoar, Ocrus, Ixion, and likely hundreds of other objects of similar size to Pluto (yet to be identified, as the Kuiper Belt and scattered disc are large search spaces) planets as well.
In order to retain the use of the word "planet" in a context that is relatively closely related to its historical usage, a line has to be drawn somewhere. It is far more logical to draw that line above Pluto than below it. If you are advocating for every object which is large enough to pull itself into hydrostatic equilibrium by gravity, and is not in orbit around another non-stellar object a planet -- you're going to have upwards of 100 of them, and that's just what we know of right now.
How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.
The New Horizons team refers to it as a planet. New Horizons head Alan Stern is one of the leading advocates for the reversal of the IAU decision. Pluto and other large KBOs have been referred to many times as planets in peer-reviewed literature since the IAU decision. One of the NASA links in this article itself refers to Pluto as a planet ("At half the diameter of Pluto, Charon is the largest satellite relative to its planet in the solar system."). Large numbers of people in the field - I'd wager a solid majority of planetary scientists (who make up only a small minority of the IAU's membership but really should be the ones making these decisions) - think the IAU seriously screwed up here. There are literally dozens of reasons why it was a screwup - need I go into them?
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Hmm.
I hate to respond to my own comment, but something just occurred to me.
That was in reference to the fact that the "water streaks" are not "water", but rather deliquescent perchlorate salts that managed to draw enough water out of the atmosphere to create damp streaks on the surface. Perchlorates are most famously used as the oxidizer in a number of rocket fuel mixtures, and seem to be very abundant in the Martian regolith, all over the planet - it makes up about half a percentage of its mass. This is of course bad for the search for life - they make a better hand sanitizer than they do a growth medium.
But could one actually use them for what we use them for on Earth - rocket fuel?
They're readily soluble - many are even deliquescent - and so should be very easy to extract with nothing more than water in a closed loop, consuming little energy (compared to the amount of energy needed to produce oxygen as an oxidizer on Mars). And the oxidizer is the heavier portion of a rocket propellant. Rather than the concept of making Mars return propellant from turning atmospheric CO2 and water-electrolysis hydrogen (or Earth-imported hydrogen**) into methane, and liquefying oxygen as an oxidizer, you could use the easy-to-extract perchlorates as your oxidizer. A clever rover wheel or tread design could scoop up regolith as it crawls, wash it, dry it, and return it in a continuous process.
Calcium perchlorate, for example, is a common Martian perchlorate - Ca(ClO4)2. It burns with hydrogen (14 H2) to produce CaO + Cl2 + 7 H2O. It burns with methane (3,5 CH4) to produce CaO + Cl2 + 3,5 CO2 + 3.5 H2O. In the former case, that's 28 AMU of hydrogen per 239 AMU of calcium perchlorate, or a ratio of 1:8.5. In the latter case, it's 14 AMU of hydrogen per 239 of calcium perchlorate, or a ratio of 1:17 - meaning you need very little hydrogen per unit mass of oxidizer (which is a very good thing!**). LOX/H2 and LOX/CH4 are, by contrast, ratios of 1:4 and 1:8, respectively. Now, using perchlorate as an oxidizer yields a propellant that's not as high ISP as using LOX, of course, but for the first stage (the heavy stage), you don't need a super-high ISP. Calcium perchlorate is 2 1/2 times denser than LOX (a huge advantage in terms of reducing tankage mass), suffers no thermal management issues at practical Martian temperatures, and being a solid rather than a liquid does not slosh. The ISP of the propellent mix can be improved by converting the calcium perchlorate to ammonium perchlorate, at a cost of complexity and additional raw materials (imported hydrogen + local Haber process or imported NH3). If a pure solid rocket is desired rather than a hybrid, methane can be polymerized with heat and catalysts to heavier hydrocarbons that will solidify when allowed to cool to Martian ambient temperatures. This process would further reduce the amount of hydrogen that needs to be imported, as hydrogen gas gets released during polymerization.
Not saying that this is the best of approaches. It's just an approach I haven't heard discussed before as far as locally produced propellants are concerned.
** While most people assume local Martian hydrogen and oxygen from electrolysis of Martian ice, this is far harder than most people assume, and not simply because mining hard materials on another world is so potentially difficult. Our history of experience with electrolysis in space has been fraught with problems (see the ISS for examples), and that's with about as tightly controlled feedstocks as you can get. On Mars you're dealing with not pure water ice, but rather frozen muck. Hence the lower-risk proposals call for using a solid oxide fuel cell to convert CO2 to CO+O2 to get the oxygen and importing the hydrogen.
Crowd: What do we want? Fry: Fry's dog! Crowd: When do we want it? Fry: Fry's dog!
Is it just me or did Earth get stuck with possibly the most boring satellite in the entire solar system?