David Appell reviews Catching Stardust: Comets, Asteroids and the Birth of the Solar System by Natalie Starkey
Comets and asteroids are the fireworks of the solar system. Ancient, mysterious, captivating, they can dazzle the night sky or bring extinctions to life on Earth. They’re like your cousin Eddie who comes to visit every so often, full of merriment and mirth, somewhat unpredictable, always with the potential to leave the household askew or in tatters.
In Catching Stardust: Comets, Asteroids and the Birth of the Solar System, Natalie Starkey shares her fascination with these visitors from beyond, detailing how scientists study comets and asteroids to understand the 4.6-billion-year history of the solar system. That history has been unfolding its wings in the last few decades, thanks to remote missions such as NASA’s Stardust, which flew from 1999 to 2016 and returned a small capsule to Earth. There has also been Rosetta, a European Space Agency voyage that ran from 2004 to 2016 and was the first to land on a comet and analyse it in situ. Catching Stardust explains what we know about these objects and how, as well as why it matters – comets may well have brought life to Earth and have nearly ended it more than once. The book also looks at what the future might hold for space mining and planetary defence from cataclysmic impacts.
Comet sightings have been recorded for almost 3000 years, first documented by the Chinese. The Greeks named them “long-haired”, from which we get the word “comet”. Sorcerers and seers held that comets and shooting stars were omens for kings and catastrophes (King Harold II died at the Battle of Hastings in 1066, the same year Halley’s comet passed by), or were harbingers of disease and death (1347’s Comet Negra was known as the “comet of black death” as the contagion broke out in England the following year). Meanwhile, the Pawnee native Americans considered shooting stars part of their stories of reincarnation.
Catching Stardust gets into the details of these extraterrestrial visitors. Where did comets and asteroids come from, and how do we know what they’re made of? How does this knowledge inform us about the history of the solar system? It examines models such as the “grand tack hypothesis” – the proposal that during the solar system’s infancy, Jupiter moved inward to 1.5 AU after its formation, and then back outward, scattering asteroids and thinning the asteroid belt. It also covers the Nice model – which proposes that early giant planets were further inward than today and nearer one another. The book asks if such models can predict or explain what’s being learned about the dynamical evolution of the solar system and the early movement of material between the inner and outer regions.
Starkey’s book finds its stride in the second half, with chapters on the Stardust mission to comet Wild 2, the first to return samples of a comet’s dust to Earth; on future space mining of asteroids; and of how humans might protect themselves from the next Extinction Level Event (ELE).
The 2014 Rosetta mission, which tenuously and dramatically put the Philae lander on Comet 67P/Churyumov–Gerasimenko, was especially full of drama. The unguided lander bounced off the surface of the duck-shaped Comet 67P twice, until coming to rest off-kilter in the shadow of a crater wall. (In fact, scientists did not spot the lander until a few years later.) This meant the lander’s solar panels failed to catch enough sunlight, so scientists had just over two days of battery power to select and prioritize what the lander could still do with the instruments available. The tension oozed.
Rendezvous with a comet
The Philae episode made for dramatic reading and viewing, and I would have preferred that Catching Stardust included some journalism there instead of straight narration. Quotes, for example, would have offered emotion and colour from the scientists and engineers on the human side of the mission 300 million miles away. As information returned from the lander, the team swivelled from victory to near defeat, working fast and furiously to achieve a partial victory in the end – Philae captured and analysed some dust on its first touchdown.
I was also surprised that neither the glossary nor index included the words “volatiles” or “Chicxulub”, the comet that killed the dinosaurs. These sections could each have been more extensive. As for Comet Shoemaker–Levy 9, whose fragments fell one after the other into Jupiter in 1994, it gets only the briefest of mentions in a picture and caption.
Starkey, a geologist and cosmochemist, did her PhD at the University of Edinburgh and postdoctoral work at the Open University. After graduating, her research interests shifted from Arctic volcanoes to comet and asteroid sampling, and she analysed samples from Stardust and the Japanese Hayabasa mission. Some of the best parts of Starkey’s book illustrate how scientists like her think, how they keep an open mind while simultaneously trying to zero in on the truth, and how uncertainties are an inherent part of the scientific process.
Sadly, there are few further missions planned to visit an asteroid or comet. NASA will send a craft to Psyche – a nickel-iron asteroid lying between Mars and Jupiter that’s thought to be the exposed core of an early protoplanet – but it will not launch until 2022. Still, I get a sense that the spring is being loaded for further forays into the solar system, at least among the inner planets. SpaceX has put a satellite in orbit and recovered the rocket, robotic spacecraft are tailing and landing on comets, China and India have planted flags on the Moon, companies have been formed to think about space mining and the SUV-sized Curiosity rover has roamed more than 20 km on the surface of Mars.
Rapid- and even real-time coverage on the Web shows these projects in their most raw and exciting states, making clear the infectious passion of the scientists and engineers who are meeting new technical challenges and viewing new worlds. The “we’re down on Mars” call when Curiosity reached the Martian surface in 2012 sent an unforgettable jolt of electricity straight down my spine. This is a great time to be a teenage space enthusiast, and this is a great book for them.
- 2018 Bloomsbury Sigma 256pp £16.99hb
