Dr. Joshua Emery

December 20, 2006

SETI Institute Principal Investigator

Ongoing discoveries of exotic planetary systems around other stars raise the questions of how these various systems form and whether they do or even can support habitats for life. In fact, it is not even clear exactly why or how life arose in our own Solar System, yet theories about the habitability of newly discovered systems around other stars will inevitably be informed by our experiences in and knowledge of our Solar System. Planetary astronomer Josh Emery seeks to understand the formation and evolution of the Solar System through observations of small bodies (asteroids, icy moons, Kuiper Belt objects) with Earth-based and space-based telescopes.

Of particular interest is learning how organic material is distributed within the Solar System. It is thought that the Earth would have formed with little organic material (the precursor molecules of life) of its own, and that the building blocks for life were supplied from outside, most likely by asteroids and/or comets crashing into the Earth. Most asteroids in the inner part of the Main Belt are known to have rocky surfaces, but many asteroids further out have a different appearance (less reflective than coal but with a red color). This dark, red appearance may be due to the presence of organic material on the surfaces, but could also be due to different silicate mineralogy (rock-type). Because of the low reflectance and large distances to these asteroids, only the largest telescopes on Earth and those in space are able to study them in detail. Using these telescopes, Dr. Emery searches in the infrared part of the electromagnetic spectrum (longer wavelengths than visible light) for signatures of the compositions of these dark asteroids.

The chemistry that occurred in the solar nebula – out of which everything in the Solar System formed – was a critical determining factor for the formation of life. Because they have been less altered since their formation than the planets have, small bodies give a direct window into this chemistry of the early solar nebula. The planets, due to their large sizes, have undergone processes (e.g., differentiation – where the heavy material sinks to the center) that have significantly changed their surface materials. Asteroids, comets, etc. never grew large enough for these changes to occur, so their current compositions are pretty much the same as when they formed. The chemistry of the inner Solar System (where the Earth formed) is fairly well understood, and does not provide the organic material necessary for life. Systematically uncovering the compositions of distant asteroids and Kuiper Belt objects (icy/rocky small bodies near the orbit of Neptune and beyond) is necessary for understanding how our Solar System formed and how it provided the pathways for life to arise and evolve. Only by understanding our own system in detail can we hope to gain a clear view of what may be awaiting us in the newly discovered systems elsewhere in the galaxy.


Joshua Emery is investigating suitable targets for space missions to Near-Earth Objects.  The Near-Earth Objects (NEOs) are small bodies of the solar system which periodically approach or intersect the Earth's orbit.  The NEO population is supposed to be continuiously replenished by asteroids and comets and is believed to be one of the principal sources of meteorites found on the Earth.  As a consequence, the study of the physical properties of NEOs is interesting for scientific goals, to investigate the nature of the whole population of small bodies of the solar system.  It also provides essential information for technological purposes, considering the potential hazard that these objects constitute to our planet and the development of suitable mitigation strategies both on Earth and from space.

In the last several years, scientific and technological goals have pushed space agencies to plan and launch space missions to NEOs.  In this respect, observations investigating the physical and thermal structure of NEOs are needed in support of future space missions.  Due to the wide variety of the orbital characteristics of NEOs, target selection must be able to guarantee both technical feasibility and high scientific return.  We therefore propose to carry out spectroscopic observations, in the mid- and far-infrared wavelength range of NEOs characterized by a high degree of accessibility for a space mission.  We have selected 13 targets accessible from Earth for space missions that amount to a total of 24.5 hours of IRS observations to obtain spectroscopic data between 5.2 and 38 microns.  The aim of these observations is the investigation of the surface composition and thermal structure, and the determination of the albedo and diameter of each selected target.

- SETI Institute Explorer, Special Edition 2006


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