Heavy Planet (63 page)
Authors: Hal Clement
The world itself is rather surprising in several ways. Its equatorial diameter is forty-eight thousand miles. From pole to pole along the axis it measures nineteen thousand seven hundred and forty, carried to more significant figures than I have any right to. It rotates on its axis at a trifle better than twenty degrees a minute, making the day some seventeen and three quarter minutes long. At the equator I would weigh about four hundred eighty pounds, since I hand-picked the net gravity there; at the poles, I’d be carrying something like sixty tons. To be perfectly frank, I don’t know the exact value of the polar gravity; the planet is so oblate that the usual rule for spheres, to the effect that one may consider all the mass concentrated at the center for purposes of computing surface gravity, would not even be a good approximation if this world were of uniform density. Having it so greatly concentrated helps a great deal, and I don’t think the rough figure of a little under seven hundred Earth gravities that I used in the story is too far out; but anyone who objects is welcome if he can back it up. (Some formulae brought to my attention rather too late to be useful suggest that I’m too high by a factor of two; but whose formulae are the rougher approximations I couldn’t guess—as I have said, my math has long since gone to a place where I can’t use it for such things. In any case, I’d still stagger a bit under a mere thirty tons.)
CROSS SECTION
of MESKLIN
of MESKLIN
Shaded portion represents Earth on the same scale. Dotted lines are arctic and antarctic circles. Listed values of gravity (effective), represented by numbers at appropriate latitudes, are very approximate.
I can even justify such a planet, after a fashion, by the current(?) theories of planetary system formation. Using these, I assume that the nucleus forming the original protoplanet had an orbit of cometary eccentricity, which was not completely rounded out by collisions during the process of sweeping up nearly all the raw material in the vicinity of its sun. During the stage when its “atmosphere” extended across perhaps several million miles of space, the capture of material from orbits which were in general more circular than its own would tend to give a spin to the forming world, since objects from outside its position at any instant would have a lower velocity than those from farther in. The rotation thus produced, and increased by conservation of angular momentum as the mass shrank, would be in the opposite direction to the world’s orbital motion. That does not bother me, though; I didn’t even mention it in the story, as nearly as I can now recall.
The rate of spin might be expected to increase to the point where matter was actually shed from the equator, so I gave the planet a set of rings and a couple of fairly massive moons. I checked the sizes of the rings against the satellite orbits, and found that the inner moon I had invented would produce two gaps in the ring similar to those in Saturn’s decoration. The point never became important in the story, but it was valuable to me as atmosphere; I had to have the picture clearly in mind to make all possible events and conversations consistent. The inner moon was ninety thousand miles from the planet’s center, giving it a period of two hours and a trifle under eight minutes. The quarterperiod and third-period ring gaps come about twelve and nineteen thousand miles respectively from the world’s surface. The half-period gap would fall about thirty-three thousand miles out, which is roughly where Roché’s Limit would put the edge of the ring anyway (I say roughly, because that limit depends on density distribution too.)
SCALE DRAWING of MESKLIN and RING SYSTEM
Inner ring reaches to less than 1,000 miles of planet’s surface; gaps are of corresponding width
.
.
On the whole, I have a rather weird-looking object. The model I have of it is six inches in diameter and not quite two and a half thick; if I added the ring, it would consist of a paper disk about fourteen inches in diameter cut to fit rather closely around the plastic wood spheroid. (The model was made to furnish something to draw a map on; I like to be consistent. The map was drawn at random before the story was written; then I bound myself to stick to the geographic limitations it showed.) I was tempted, after looking at it for a while, to call the book
Pancake in the Sky,
but Isaac Asimov threatened violence.
3
Anyway, it looks rather more like a fried egg.
Pancake in the Sky,
but Isaac Asimov threatened violence.
3
Anyway, it looks rather more like a fried egg.
There are a lot of characteristics other than size, though, which must be settled before a story can be written. Since I want a native life form, I must figure out just what conditions that form must be able to stand. Some of these conditions, like the temperature and gravity, are forced on me; others, perhaps, I can juggle to suit myself. Let’s see.
Temperature depends, almost entirely, on how much heat a planet receives and retains from its sun. 61 Cygni is a binary system, but the two stars are so
far apart that I needn’t consider the other one as an influence on this planet’s temperature; and the one which it actually circles is quite easy to allow for. Several years ago I computed, partly for fun and partly for cases like this, a table containing some interesting information for all the stars within five parsecs for which I could secure data. The information consists of items such as the distance at which an Earth-type planet would have to revolve from the star in question to have the present temperatures of Earth, Venus, and Mars, and how long it would take a planet to circle the sun in question in each such orbit. For 61 Cygni A, the three distances are about twenty-eight, thirty-nine, and sixty-nine million miles, respectively. As we have seen, 61 C’s orbit is reasonably well known; and it is well outside any of those three distances. At its closest—and assuming that the primary star is 61 A—it gets almost near enough to be warmed to be about fifty below zero, Centigrade.
4
At the other end of its rather eccentric orbit, Earth at least would cool to about minus one hundred eighty, and it’s rather unlikely that this world we are discussing gets too much more out of the incoming radiation. That is a rather wide temperature fluctuation.
far apart that I needn’t consider the other one as an influence on this planet’s temperature; and the one which it actually circles is quite easy to allow for. Several years ago I computed, partly for fun and partly for cases like this, a table containing some interesting information for all the stars within five parsecs for which I could secure data. The information consists of items such as the distance at which an Earth-type planet would have to revolve from the star in question to have the present temperatures of Earth, Venus, and Mars, and how long it would take a planet to circle the sun in question in each such orbit. For 61 Cygni A, the three distances are about twenty-eight, thirty-nine, and sixty-nine million miles, respectively. As we have seen, 61 C’s orbit is reasonably well known; and it is well outside any of those three distances. At its closest—and assuming that the primary star is 61 A—it gets almost near enough to be warmed to be about fifty below zero, Centigrade.
4
At the other end of its rather eccentric orbit, Earth at least would cool to about minus one hundred eighty, and it’s rather unlikely that this world we are discussing gets too much more out of the incoming radiation. That is a rather wide temperature fluctuation.
The eccentricity of the orbit is slightly helpful, though. As Kepler’s laws demand, the world spends relatively little time close to its sun; about four fifths of its year it is outside the minus one hundred fifty degree isotherm, and it is close enough to be heated above minus one hundred for only about one hundred thirty days of its eighteen-hundred-day year—Earth days, of course. Its year uses up around one hundred forty-five thousand of its own days, the way we’ve set it spinning. For practical purposes, then, the temperature will be around minus one hundred seventy Centigrade most of the time. We’ll dispose of the rest of the year a little later.
Presumably any lifeform at all analogous to our own will have to consist largely of some substance which will remain liquid in its home planet’s temperature range. In all probability, the substance in question would be common enough on the planet to form its major liquid phase. If that is granted, what substance will meet our requirements?
Isaac Asimov and I spent a pleasant evening trying to find something that would qualify. We wanted it not only liquid within our temperature limits, but a good solvent and reasonably capable of causing ionic dissociation of polar molecules dissolved in it. Water, of course, was out; on this world it is strictly a mineral. Ammonia is almost as bad, melting only on the very hottest days. We played with ammonia’s analogues from further along the periodic table—phosphine, arsine, and stibine—with carbon disulfide and phosgene, with carbon suboxide and hydrogen fluoride, with saturated and unsaturated hydrocarbons
both straight and with varying degrees of chlorine and fluorine substitution, and even with a silicone or two. A few of these met the requirements as to melting and boiling points; some may even have caused dissociation of their solutes, though we had no data on that point for most. However, we finally fell back on a very simple compound.
both straight and with varying degrees of chlorine and fluorine substitution, and even with a silicone or two. A few of these met the requirements as to melting and boiling points; some may even have caused dissociation of their solutes, though we had no data on that point for most. However, we finally fell back on a very simple compound.
It boils, unfortunately, at an inconveniently low temperature, even though we assume a most unlikely atmospheric pressure. It cannot be expected to be fruitful in ions, though as a hydrocarbon it will probably dissolve a good many organic substances. It has one great advantage, though, from my viewpoint; it would almost certainly be present on the planet in vast quantities. The substance is methane—CH
4
.
4
.
Like Jupiter, this world must have started formation with practically the “cosmic” composition, involving from our viewpoint a vast excess of hydrogen. The oxygen present would have combined with it to form water; the nitrogen, to form ammonia; the carbon to form methane and perhaps higher hydrocarbons. There would be enough hydrogen for all, and plenty to spare—light as it is, even hydrogen would have a hard time escaping from a body having five thousand times the mass of Earth once it had cooled below red heat—at first, that is. Later, when the rotational velocity increased almost to the point of real instability, it would be a different story; but we’ll consider that in a moment. However, we have what seems to be a good reason to expect oceans of methane on this world; and with such oceans, it would be reasonable to expect the appearance and evolution of life forms using that liquid in their tissues.
But just a moment. I admitted a little while ago that methane boils at a rather lower temperature than I wanted for this story. Is it
too
low? Can I raise it sufficiently by increasing the atmospheric pressure, perhaps? Let’s see. The handbook lists methane’s critical temperature as about minus eighty-two degrees Centigrade. Above that temperature it will always be a gas, regardless of pressure; and to bring its boiling point up nearly to that value, a pressure about forty-six times that of our own atmosphere at sea level will be needed. Well, we have a big planet, which should have held on to a lot of its original gases; it ought to have a pressure of hundreds or even thousands of atmospheres—whoops! we forgot something.
too
low? Can I raise it sufficiently by increasing the atmospheric pressure, perhaps? Let’s see. The handbook lists methane’s critical temperature as about minus eighty-two degrees Centigrade. Above that temperature it will always be a gas, regardless of pressure; and to bring its boiling point up nearly to that value, a pressure about forty-six times that of our own atmosphere at sea level will be needed. Well, we have a big planet, which should have held on to a lot of its original gases; it ought to have a pressure of hundreds or even thousands of atmospheres—whoops! we forgot something.
At the equator,
effective
gravity—gravity minus centrifugal effect—is three times Earth normal. That, plus our specification of temperature and composition of the atmosphere, lets us compute the rate at which atmospheric density will decrease with altitude. It turns out that with nearly pure hydrogen, three g’s, and a temperature of minus one hundred fifty for convenience, there is still a significant amount of atmosphere at six-hundred-miles altitude if we start at forty-odd bars for surface pressure—
and at six hundred miles above the equator of this planet the centrifugal force due to its rotation balances the gravity!
If there had ever been a significant amount of atmosphere at that height, it would long since have been slung away into space; evidently we cannot possibly have a surface
pressure anywhere near forty-six atmospheres. Some rough slide-rule work suggests eight atmospheres as an upper limit—I used summer temperatures rather than the annual mean.
effective
gravity—gravity minus centrifugal effect—is three times Earth normal. That, plus our specification of temperature and composition of the atmosphere, lets us compute the rate at which atmospheric density will decrease with altitude. It turns out that with nearly pure hydrogen, three g’s, and a temperature of minus one hundred fifty for convenience, there is still a significant amount of atmosphere at six-hundred-miles altitude if we start at forty-odd bars for surface pressure—
and at six hundred miles above the equator of this planet the centrifugal force due to its rotation balances the gravity!
If there had ever been a significant amount of atmosphere at that height, it would long since have been slung away into space; evidently we cannot possibly have a surface
pressure anywhere near forty-six atmospheres. Some rough slide-rule work suggests eight atmospheres as an upper limit—I used summer temperatures rather than the annual mean.
At that pressure methane boils at about minus one hundred forty-three degrees, and for some three hundred Earth days, or one-sixth of each year, the planet will be in a position where its sun could reasonably be expected to boil its oceans. What to do?
Well, Earth’s mean temperature is above the melting point of water, but considerable areas of our planet are permanently frozen. There is no reason why I can’t use the same effects for 61 C; it is an observed fact that the axis of rotation of a planet can be oriented so that the equatorial and orbital planes do not coincide. I chose for story purposes to incline them at an angle of twenty-eight degrees, in such a direction that the northern hemisphere’s midsummer occurs when the world is closest to its sun. This means that a large part of the northern hemisphere will receive no sunlight for fully three quarters of the year, and should in consequence develop a very respectable cap of frozen methane at the expense of the oceans in the other hemisphere. As the world approaches its sun the livable southern hemisphere is protected by the bulk of the planet from its deadly heat output; the star’s energy is expended in boiling off the north polar “ice” cap. Tremendous storms rage across the equator carrying air and methane vapor at a temperature little if any above the boiling point of the latter; and while the southern regions will warm up during their winter, they should not become unendurable for creatures with liquid methane in their tissues.
Other books
A Perfect Day by Richard Paul Evans
I Heart Geeks by Aria Glazki, Stephanie Kayne, Kristyn F. Brunson, Layla Kelly, Leslie Ann Brown, Bella James, Rae Lori
Exposed: Misbehaving with the Magnate by Kelly Hunter
Angel In My Bed by Melody Thomas
Things No One Will Tell Fat Girls by Jes Baker
Temporary Husband by Day Leclaire
Chain of Shadows (Blood Skies, Book 6) by Montano, Steven
A Future for Three by Rachel Clark
Desperate Hearts by Rosanne Bittner
The Blood Crows (Roman Legion 12) by Scarrow, Simon
