Books by Carroll, Michael

Carroll, Michael. Living Among Giants. Cham, Switzerland: Springer International, 2015. ISBN 978-3-319-10673-1.
In school science classes, we were taught that the solar system, our home in the galaxy, is a collection of planets circling a star, along with assorted debris (asteroids, comets, and interplanetary dust). Rarely did we see a representation of either the planets or the solar system to scale, which would allow us to grasp just how different various parts of the solar system are from another. (For example, Jupiter is more massive than all the other planets and their moons combined: a proud Jovian would probably describe the solar system as the Sun, Jupiter, and other detritus.)

Looking more closely at the solar system, with the aid of what has been learned from spacecraft exploration in the last half century, results in a different picture. The solar system is composed of distinct neighbourhoods, each with its own characteristics. There are four inner “terrestrial” or rocky planets: Mercury, Venus, Earth, and Mars. These worlds huddle close to the Sun, bathing in its lambent rays. The main asteroid belt consists of worlds like Ceres, Vesta, and Pallas, all the way down to small rocks. Most orbit between Mars and Jupiter, and the feeble gravity of these bodies and their orbits makes it relatively easy to travel from one to another if you're patient.

Outside the asteroid belt is the domain of the giants, which are the subject of this book. There are two gas giants: Jupiter and Saturn, and two ice giants: Uranus and Neptune. Distances here are huge compared to the inner solar system, as are the worlds themselves. Sunlight is dim (at Saturn, just 1% of its intensity at Earth, at Neptune 1/900 that at Earth). The outer solar system is not just composed of the four giant planets: those planets have a retinue of 170 known moons (and doubtless many more yet to be discovered), which are a collection of worlds as diverse as anywhere else in the domain of the Sun: there are sulfur-spewing volcanos, subterranean oceans of salty water, geysers, lakes and rain of hydrocarbons, and some of the most spectacular terrain and geology known. Jupiter's moon Ganymede is larger than the planet Mercury, and appears to have a core of molten iron, like the Earth.

Beyond the giants is the Kuiper Belt, with Pluto its best known denizen. This belt is home to a multitude of icy worlds—statistical estimates are that there may be as many as 700 undiscovered worlds as large or larger than Pluto in the belt. Far more distant still, extending as far as two light-years from the Sun, is the Oort cloud, about which we know essentially nothing except what we glean from the occasional comet which, perturbed by a chance encounter or passing star, plunges into the inner solar system. With our present technology, objects in the Oort cloud are utterly impossible to detect, but based upon extrapolation from comets we've observed, it may contain trillions of objects larger than one kilometre.

When I was a child, the realm of the outer planets was shrouded in mystery. While Jupiter, Saturn, and Uranus can be glimpsed by the unaided eye (Uranus, just barely, under ideal conditions, if you know where to look), and Neptune can be spotted with a modest telescope, the myriad moons of these planets were just specks of light through the greatest of Earth-based telescopes. It was not until the era of space missions to these worlds, beginning with the fly-by probes Pioneer and Voyager, then the orbiters Galileo and Cassini, that the wonders of these worlds were revealed.

This book, by science writer and space artist Michael Carroll, is a tourist's and emigrant's guide to the outer solar system. Everything here is on an extravagant scale, and not always one hospitable to frail humans. Jupiter's magnetic field is 20,000 times stronger than that of Earth and traps radiation so intense that astronauts exploring its innermost large moon Io would succumb to a lethal dose of radiation in minutes. (One planetary scientist remarked, “You need to have a good supply of grad students when you go investigate Io.”) Several of the moons of the outer planets appear to have oceans of liquid water beneath their icy crust, kept liquid by tidal flexing as they orbit their planet and interact with other moons. Some of these oceans may contain more water than all of the Earth's oceans. Tidal flexing may create volcanic plumes which inject heat and minerals into these oceans. On Earth, volcanic vents on the ocean floor provide the energy and nutrients for a rich ecosystem of life which exists independent of the Sun's energy. On these moons—who knows? Perhaps some day we shall explore these oceans in our submarines and find out.

Saturn's moon Titan is an amazing world. It is larger than Mercury, and has an atmosphere 50% denser than the Earth's, made up mostly of nitrogen. It has rainfall, rivers, and lakes of methane and ethane, and at its mean temperature of 93.7°K, water ice is a rock as hard as granite. Unique among worlds in the solar system, you could venture outside your space ship on Titan without a space suit. You'd need to dress very warmly, to be sure, and wear an oxygen mask, but you could explore the shores, lakes, and dunes of Titan protected only against the cold. With the dense atmosphere and gravity just 85% of that of the Earth's Moon, you might be able to fly with suitable wings.

We have had just a glimpse of the moons of Uranus and Neptune as Voyager 2 sped through their systems on its way to the outer darkness. Further investigation will have to wait for orbiters to visit these planets, which probably will not happen for nearly two decades. What Voyager 2 saw was tantalising. On Uranus's moon Miranda, there are cliffs 14 km high. With the tiny gravity, imagine the extreme sports you could do there! Neptune's moon Triton appears to be a Kuiper Belt object captured into orbit around Neptune and, despite its cryogenic temperature, appears to be geologically active.

There is no evidence for life on any of these worlds. (Still, one wonders about those fish in the dark oceans.) If barren, “all these worlds are ours”, and in the fullness of time we shall explore, settle, and exploit them to our own ends. The outer solar system is just so much bigger and more grandiose than the inner. It's as if we've inhabited a small island for all of our history and, after making a treacherous ocean voyage, discovered an enormous empty continent just waiting for us. Perhaps in a few centuries residents of these remote worlds will look back toward the Sun, trying to spot that pale blue dot so close to it where their ancestors lived, and remark to their children, “Once, that's all there was.”

March 2015 Permalink

Carroll, Michael. On the Shores of Titan's Farthest Sea. Cham, Switzerland: Springer International, 2015. ISBN 978-3-319-17758-8.
By the mid-23rd century, humans have become a spacefaring species. Human settlements extend from the Earth to the moons of Jupiter, Mars has been terraformed into a world with seas where people can live on the surface and breathe the air. The industries of Earth and Mars are supplied by resources mined in the asteroid belt. High-performance drive technologies, using fuels produced in space, allow this archipelago of human communities to participate in a system-wide economy, constrained only by the realities of orbital mechanics. For bulk shipments of cargo, it doesn't matter much how long they're in transit, as long as regular deliveries are maintained.

But whenever shipments of great value traverse a largely empty void, they represent an opportunity to those who would seize them by force. As in the days of wooden ships returning treasure from the New World to the Old on the home planet, space cargo en route from the new worlds to the old is vulnerable to pirates, and an arms race is underway between shippers and buccaneers of the black void, with the TriPlanet Bureau of Investigation (TBI) finding itself largely a spectator and confined to tracking down the activities of criminals within the far-flung human communities.

As humanity expands outward, the frontier is Titan, Saturn's largest moon, and the only moon in the solar system to have a substantial atmosphere. Titan around 2260 is much like present-day Antarctica: home to a variety of research stations operated by scientific agencies of various powers in the inner system. Titan is much more interesting than Antarctica, however. Apart from the Earth, it is the only solar system body to have natural liquids on its surface, with a complex cycle of evaporation, rain, erosion, rivers, lakes, and seas. The largest sea, Kraken Mare, located near the north pole, is larger than Earth's Caspian Sea. Titan's atmosphere is half again as dense as that of Earth, and with only 14% of Earth's gravity, it is possible for people to fly under their own muscle power.

It's cold: really cold. Titan receives around one hundredth the sunlight as the Earth, and the mean temperature is around −180 °C. There is plenty of water on Titan, but at these temperatures water is a rock as hard as granite, and it is found in the form of mountains and boulders on the surface. But what about the lakes? They're filled with a mixture of methane and ethane, hydrocarbons which can exist in either gaseous or liquid form in the temperature range and pressure on Titan. Driven by ultraviolet light from the Sun, these hydrocarbons react with nitrogen and hydrogen in the atmosphere to produce organic compounds that envelop the moon in a dense layer of smog and rain out, forming dunes on the surface. (Here “organic” is used in the chemist's sense of denoting compounds containing carbon and does not imply they are of biological origin.)

Mayda Research Station, located on the shore of Kraken Mare, hosts researchers in a variety of fields. In addition to people studying the atmosphere, rivers, organic compounds on the surface, and other specialties, the station is home to a drilling project intended to bore through the ice crust and explore the liquid water ocean believed to lie below. Mayda is an isolated station, with all of the interpersonal dynamics one expects to find in such environments along with the usual desire of researchers to get on with their own work. When a hydrologist turns up dead of hypothermia—frozen to death—in his bed in the station, his colleagues are baffled and unsettled. Accidents happen, but this is something which simply doesn't make any sense. Nobody can think of either a motive for foul play nor a suspect. Abigail Marco, an atmospheric scientist from Mars and friend of the victim, decides to investigate further, and contacts a friend on Mars who has worked with the TBI.

The death of the scientist is a mystery, but it is only the first in a series of enigmas which perplex the station's inhabitants who see, hear, and experience things which they, as scientists, cannot explain. Meanwhile, other baffling events threaten the survival of the crew and force Abigail to confront part of her past she had hoped she'd left on Mars.

This is not a “locked station mystery” although it starts out as one. There is interplanetary action and intrigue, and a central puzzle underlying everything that occurs. Although the story is fictional, the environment in which it is set is based upon our best present day understanding of Titan, a world about which little was known before the arrival of the Cassini spacecraft at Saturn in 2004 and the landing of its Huygens probe on Titan the following year. A twenty page appendix describes the science behind the story, including the environment at Titan, asteroid mining, and terraforming Mars. The author's nonfiction Living Among Giants (March 2015) provides details of the worlds of the outer solar system and the wonders awaiting explorers and settlers there.

December 2016 Permalink