How Asteroids Shaped Earth

"In this book, early fluent readers will learn about asteroids, their composition, how they have changed Earth's landscape, and how they could change the future of life on Earth and in space"--

Asteroids are diverse and numerous solar system objects, from the large number of objects in the main asteroid belt to the relatively small near-Earth population. Understanding their physical properties is essential to understanding the evolution of the solar system, and asteroid morphology is a complex field in its own right. The histories of individual asteroids, and particularly near-Earth objects, reflect continuous interaction among their shapes, rotation states, and orbits due to the effects of radiation pressure. Radar astronomy has provided detailed information on the orbits, sizes, shapes, rotation states, and composition of many asteroids. To improve the capabilities of asteroid radar observations, I have developed the technique of radar speckle tracking. The echoes from different points on the surface of a radar target interfere with each other, producing a pattern of bright and dark speckles across the surface of the Earth. Using radio astronomy techniques, I track the motion of speckles between several ground stations during a radar experiment to accurately determine the rotation state of the target. Speckle tracking is a powerful tool both to determine the orbital evolution of near-Earth asteroids, particularly potential Earth impactors, and to survey the overall physical properties of the asteroid population. In addition, I have studied applying the techniques of adaptive optics and radio interferometry to asteroid science. These will become more useful with the next generation of asteroid-detecting surveys and the construction of large sub-millimeter interferometers. Interferometry in particular will soon be able to survey the entire asteroid belt.

Comets and asteroids are in some sense the fossils of the solar system. They have avoided most of the drastic physical processing that shaped the planets and thus represent more closely the properties of the primordial solar nebula. What processing has taken place is itself of interest in decoding the history of our solar neighborhood. Near-Earth objects are also of interest because one or more large ones have been blamed for the rare but devastating events that caused mass extinctions of species on our planet, as attested by recent excitement over the impending passage of asteroid 1997 XF11. The comets and asteroids whose orbits bring them close to Earth are clearly the most accessible to detailed investigation, both from the ground and from spacecraft. When nature kindly delivers the occasional asteroid to the surface of Earth as a meteorite, we can scrutinize it closely in the laboratory; a great deal of information about primordial chemical composition and primitive processes has been gleaned from such objects. This report reviews the current state of research on near-Earth objects and considers future directions. Attention is paid to the important interplay between ground-based investigations and spaceborne observation or sample collection and return. This is particularly timely since one U.S. spacecraft is already on its way to rendezvous with a near-Earth object, and two others plus a Japanese mission are being readied for launch. In addition to scientific issues, the report considers technologies that would enable further advances in capability and points out the possibilities for including near-Earth objects in any future expansion of human exploration beyond low Earth orbit.

'A promising debut.' New Scientist Icy, rocky, sometimes dusty, always mysterious – comets and asteroids are among the Solar System's very oldest inhabitants, formed within a swirling cloud of gas and dust in the area of space that eventually hosted the Sun and its planets. Locked within each of these extra-terrestrial objects is the 4.6-billion-year wisdom of Solar System events, and by studying them at close quarters using spacecraft we can coerce them into revealing their closely-guarded secrets. This offers us the chance to answer some fundamental questions about our planet and its inhabitants. Exploring comets and asteroids also allows us to shape the story of Earth's future, enabling us to protect our precious planet from the threat of a catastrophic impact from space, and maybe to even recover valuable raw materials from them. This cosmic bounty could be as useful in space as it is on Earth, providing the necessary fuel and supplies for humans as they voyage into deep space to explore more distant locations within the Solar System. Catching Stardust tells the story of these enigmatic celestial objects, revealing how scientists are using them to help understand a crucial time in our history – the birth of the Solar System, and everything contained within it.

"Asteroids come in all shapes and sizes--and hit our planet in them, too. But what happens if a catastrophically large one approaches earth? By looking on the ground at historical asteroid craters and present-day falls, and up into space for the big ones yet to come, a wide variety of scientists are trying to figure out how to track asteroids--and how to avoid devastating impacts in the future."--

This book develops a general approach that can be systematically refined to investigate the statics and dynamics of deformable solid bodies. These methods are then employed to small bodies in the Solar System. With several space missions underway and more being planned, interest in our immediate neighbourhood is growing. In this spirit, this book investigates various phenomena encountered in planetary science, including disruptions during planetary fly-bys, equilibrium shapes and stability of small rubble bodies, and spin-driven shape changes. The flexible procedure proposed here will help readers gain valuable insights into the mechanics of solar system bodies, while at the same time complementing numerical investigations. The technique itself is built upon the virial method successfully employed by Chandrasekhar (1969) to study the equilibrium shapes of spinning fluid objects. However, here Chandrasekhar’s approach is modified in order to study more complex dynamical situations and include objects of different rheologies, e.g., granular aggregates, or “rubble piles”. The book is largely self-contained, though some basic familiarity with continuum mechanics will be beneficial.

This series will make readers wonder what might happen if particular events occurred. Grounded in fact, each book assesses the possibility or threat of an event, from melting ice caps to a fuel shortage. Each book also offers suggestions on how to respond to these environmental and ecological challenges before it's too late.

"More than forty chapters detail our current astronomical, compositional, geological, and geophysical knowledge of asteroids, as well as their unique physical processes and interrelationships with comets and meteorites"--Provided by publisher.