Plot summary
A consortium of spacefaring races, including humans, recruits Mesklinites, the centipede-like natives of the high-gravity planet Mesklin, to explore Dhrawn. The recruits include Barlennan and Dondragmer, respectively the Captain and First Mate of the Bree, a merchant vessel of Mesklin, which in Mission of Gravity sailed to Mesklin's south pole to rescue a probe sent by humans. Now, thanks to institutes of learning set up on Mesklin, the natives have produced capable explorers who can go where other races cannot.
Barlennan is in command of the main base on Dhrawn while Dondragmer commands a "land cruiser", the Kwembly. This is a tracked vehicle about 30 meters long, 6 meters high and the same wide. It is designed to move like a large worm on independently steerable trucks. The power is supplied by self-contained fusion generators but the controls are simple pulley-and-rope systems using Mesklinite materials which the crew can repair by themselves. There are several more cruisers, and each has audio/video links for communication with satellites.
The humans and others are on a satellite in synchronous orbit above the explorers on the ground. Unfortunately, the planet's slow rotation means that they are about 10 million kilometres above the surface, and signals take over 30 seconds to travel to the satellite. Real-time conversations are therefore impossible.
On the satellite are linguist "Easy" Hoffman and her son Benj, who is both an engineer and a linguist. Both speak fluent Stennish, the Mesklinite language, and have formed close personal relationships with the explorers on the surface. They are later joined on the satellite by Ib Hoffman, Easy's husband and Benj's father.
One of the cruisers, the Esket, has apparently suffered a catastrophe and all the crew have vanished, much to Easy's dismay. The cruiser's communicators still function, but all they show are views of a deserted ship.
In reality, Barlennan is executing a complicated deception. A wily negotiator who successfully coerced the humans into setting up a College to teach science to the Mesklinites in Mission of Gravity, he has been secretly arranging for an independent Mesklinite colony to be set up on Dhrawn using the Esket as a base. This has been proceeding successfully for several months.
Soon, however, the Kwembly is in very real trouble. As the planet warms, the complex phase transitions of water and ammonia mixtures at these low temperatures mean that a frozen lake can melt in seconds, carry the ship off in a flood, and equally suddenly leave it hung up on large rocks, unable to move as the liquid around it freezes again, trapping some of the crew below the surface in their protective suits.
A few of the Kwembly's crew are dispatched to report on the condition of the surroundings, but come across one of the crew from the Esket, who is doing likewise in one of the dirigibles that Barlennan is clandestinely using to move his men and matériel around. He momentarily appears on a screen and is recognized by Easy. While the other humans believe that she is mistaken, Ib begins to suspect that something underhanded is going on.
The Hoffmans would prefer to deal honestly with the Mesklinites, but they have to deal with the prejudices, not only of fellow humans with political motives, but with the more paranoid of the non-human supervisors of the mission. Having an inkling of what Barlennan is really after, to have his people learn to fly starships and eventually explore the galaxy in their own right, Ib finally convinces the human administrators that they should treat the bug-like creatures as equals rather than hired hands.
The novel ends with the Mesklinite colonies receiving clandestine help and communication with the Hoffmans, but it is not revealed whether Barlennan's machinations remain secret from the other humans.
Themes
The main theme revolves around hard science, particularly the physics and thermodynamics of mixtures. While water should be in the form of ice at all times on Dhrawn, the effect of ammonia in the atmosphere is to cause it to become a liquid under certain conditions of temperature and pressure, because of the formation of a eutectic mixture which melts and freezes at a much lower temperature than water. Although the scientists on the satellite attempt to supply weather forecasts for the Mesklinites, they are using tools designed for Earth's weather to predict conditions in a two-component water/ammonia system instead of Earth's one-component system. Even local effects, such as liberation of latent heat from mixtures undergoing freezing or condensation, can produce drastic changes in conditions. Seemingly solid surfaces can liquefy under the pressure of the land cruisers, even as individual Mesklinites can walk on them in complete safety.
The novel posits that full disclosure is best in a situation where unpredictable changes can occur. Ib Hoffman relates the story of how his son Benj, at the age of thirteen, designed and built SCUBA equipment, carefully calculating all the parameters, only to come close to dying on his first dive because he lacked a crucial piece of information about the physiology of breathing, one which all his knowledge of physics and engineering could not have predicted.
Harry Clement Stubbs, better known by the pen name Hal Clement, was an American science fiction writer and a leader of the hard science fiction subgenre. He also painted astronomically oriented artworks under the name George Richard.
Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System. Uncrewed space probes have flown to all the observed planets in the Solar System as well as to dwarf planets Pluto and Ceres, and several asteroids. Orbiters and landers return more information than fly-by missions. Crewed flights have landed on the Moon and have been planned, from time to time, for Mars, Venus and Mercury. While many scientists appreciate the knowledge value that uncrewed flights provide, the value of crewed missions is more controversial. Science fiction writers propose a number of benefits, including the mining of asteroids, access to solar power, and room for colonization in the event of an Earth catastrophe.
Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is currently carried out mainly by astronomers with telescopes, its physical exploration is conducted both by uncrewed robotic space probes and human spaceflight. Space exploration, like its classical form astronomy, is one of the main sources for space science.
Space colonization is the use of outer space or celestial bodies other than Earth for permanent habitation or as extraterrestrial territory.
An atmosphere is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules.
Titania, also designated Uranus III, is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of 1,578 kilometres (981 mi), with a surface area comparable to that of Australia. Discovered by William Herschel in 1787, it is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream. Its orbit lies inside Uranus' magnetosphere.
Mesklin is a fictional supergiant planet created by Hal Clement and used in a number of his hard science fiction stories.
The Case for Mars: The Plan to Settle the Red Planet and Why We Must is a nonfiction science book by Robert Zubrin, first published in 1996, and revised and updated in 2011.
Mission of Gravity is a science fiction novel by American writer Hal Clement. The novel was serialized in Astounding Science Fiction magazine in April–July 1953. Its first hardcover book publication was in 1954, and it was first published as a paperback book in 1958. Along with the novel, many editions of the book also include "Whirligig World", an essay by Clement on creating the planet Mesklin that was first published in the June 1953 Astounding.
Aerocapture is an orbital transfer maneuver in which a spacecraft uses aerodynamic drag force from a single pass through a planetary atmosphere to decelerate and achieve orbit insertion.
The colonization of Venus has been a subject of many works of science fiction since before the dawn of spaceflight, and is still discussed from both a fictional and a scientific standpoint. However, with the discovery of Venus's extremely hostile surface environment, attention has largely shifted towards the colonization of the Moon and Mars instead, with proposals for Venus focused on habitats floating in the upper-middle atmosphere and on terraforming.
Saturn's largest moon Titan is one of several candidates for possible future colonization of the outer Solar System, though protection against extreme cold is a major consideration.
The terraforming of Mars or the terraformation of Mars is a hypothetical procedure that would consist of a planetary engineering project or concurrent projects aspiring to transform Mars from a planet hostile to terrestrial life to one that could sustainably host humans and other lifeforms free of protection or mediation. The process would involve the modification of the planet's extant climate, atmosphere, and surface through a variety of resource-intensive initiatives, as well as the installation of a novel ecological system or systems.
The atmosphere of Venus is primarily of supercritical carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K, and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) underwater on Earth. The Venusian atmosphere supports opaque clouds of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts.
The exploration of Jupiter has been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2023, has continued with eight further spacecraft missions in the vicinity of Jupiter. All of these missions were undertaken by the National Aeronautics and Space Administration (NASA), and all but two were flybys taking detailed observations without landing or entering orbit. These probes make Jupiter the most visited of the Solar System's outer planets as all missions to the outer Solar System have used Jupiter flybys. On 5 July 2016, spacecraft Juno arrived and entered the planet's orbit—the second craft ever to do so. Sending a craft to Jupiter is difficult, mostly due to large fuel requirements and the effects of the planet's harsh radiation environment.
An ocean world, ocean planet, panthalassic planet, maritime world, water world or aquaplanet, is a type of planet that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, either beneath the surface, as subsurface oceans, or on the surface, potentially submerging all dry land. The term ocean world is also used sometimes for astronomical bodies with an ocean composed of a different fluid or thalassogen, such as lava, ammonia or hydrocarbons. The study of extraterrestrial oceans is referred to as planetary oceanography.
"Lecture Demonstration" is a science fiction short story by American writer Hal Clement. It was first published in Astounding: The John W Campbell Memorial Anthology in 1973.
Mars to Stay missions propose astronauts sent to Mars for the first time should intend to stay. Unused emergency return vehicles would be recycled into settlement construction as soon as the habitability of Mars becomes evident to the initial pioneers. Mars to Stay missions are advocated both to reduce cost and to ensure permanent settlement of Mars. Among many notable Mars to Stay advocates, former Apollo astronaut Buzz Aldrin has been particularly outspoken, suggesting in numerous forums "Forget the Moon, Let’s Head to Mars!" and, in June 2013, Aldrin promoted a crewed mission "to homestead Mars and become a two-planet species". In August 2015, Aldrin, in association with the Florida Institute of Technology, presented a "master plan", for NASA consideration, for astronauts, with a "tour of duty of ten years", to colonize Mars before the year 2040. The Mars Underground, Mars Homestead Project / Mars Foundation, Mars One, and Mars Artists Community advocacy groups and business organizations have also adopted Mars to Stay policy initiatives.
Planetary oceanography also called astro-oceanography or exo-oceanography is the study of oceans on planets and moons other than Earth. Unlike other planetary sciences like astrobiology, astrochemistry and planetary geology, it only began after the discovery of underground oceans in Saturn's moon Titan and Jupiter's moon Europa. This field remains speculative until further missions reach the oceans beneath the rock or ice layer of the moons. There are many theories about oceans or even ocean worlds of celestial bodies in the Solar System, from oceans made of diamond in Neptune to a gigantic ocean of liquid hydrogen that may exist underneath Jupiter's surface.
A Mars suit or Mars space suit is a space suit for EVAs on the planet Mars. Compared to a suit designed for space-walking in the near vacuum of low Earth orbit, Mars suits have a greater focus on actual walking and a need for abrasion resistance. Mars' surface gravity is 37.8% of Earth's, approximately 2.3 times that of the Moon, so weight is a significant concern, but there are fewer thermal demands compared to open space. At the surface the suits would contend with the atmosphere of Mars, which has a pressure of about 0.6 to 1 kilopascal. On the surface, radiation exposure is a concern, especially solar flare events, which can dramatically increase the amount of radiation over a short time.
