The Intensifying Search for Life on Other Planets

By Evan Schneider

     What’s being implemented to advance discovery of Earthlike planets existing in “habitable zones,” near enough to their stars for warmth but far enough away to support life? What’s needed to create the perfect environment for the creation and development of life? How can we identify these worlds in our own solar system, the Milky Way or deep into the universe?

     On June 14, James F. Kasting, professor of geosciences at Penn State, speaking at the Hayden, sought to answer many of these questions. His new book, “How to Find a Habitable Planet” (Princeton University Press, $29.95), provides a perspective on how best to utilize technology to find life on other worlds.  

     Kasting discussed recent history and hypotheses of several well-known authors in this field, then brought his audience to the present, sharing methodologies being used and planned to seek life on other worlds. 

     The lecture began with a review of several authors. James Lovelock, scientist, inventor at NASA and environmentalist, posits in “Gaia: A New Look at Life on Earth” and “Ages of Gaia” that the biosphere regulates our environment that acts to sustain life. Peter Ward, paleontologist and professor of biology, and Earth and Space Sciences at the University of Washington, asserts in “The Medea Hypothesis” that complex life is rare in the universe and that life itself is actually harmful to Earth. 

     These perspectives show how life developed on Earth and its sustainability, but their hypotheses don’t explore the possibility or extent of life on a universal scale. Kasting’s new book responds to Ward’s “Rare Earth,” which questioned Carl Sagan in his belief that extraterrestrial civilizations number in the millions. 

     Kasting showed how today’s science is being used to measure light spectra and characteristics of exoplanets to quantify data supporting parameters for life. Much of NASA is seeking life on Mars. While studying Jupiter, the Galileo probe scrutinized Europa, with its icy surface and liquid-water subsurface, suggesting the possibility of other life in our solar system.

     Today, Kasting observed, telescopes and spacecraft are measuring the radial velocity of light to calculate the speed and mass of distant planets (www.exoplanets.org). The Kepler telescope mission looks for habitable planets more than 2,000 light-years away, monitoring the brightness of 150,000 stars while waiting to identify planets that may sustain life. Once identified, reflected light from a planet can be observed, providing a chemical-composition analysis of its atmosphere and possible planetary biology.

     New and future technologies are being planned and deployed to meet NASA’s goals. The astrometric method, in calculating the mass of a planet, determines the ability to sustain life. NASA, Northrop Grumman and JPL are developing the Space Interferometry Mission Lite telescope, scheduled to launch in 2015. It will use optical interferometry (two mirrors collecting light) to hunt for exoplanets, map the Milky Way and assist in determining spatial distribution of dark matter.    

     Large space-based telescopes will use direct imaging to observe planetary spectra. The James Webb Space Telescope, launching in 2014, will use infrared equipment to peer through dusty clouds of our galaxy to look for galaxies formed in the early universe. This may help to explain the evolution of planets and their relationship to stars, supporting the exoplanet search.

     Direct imaging also has the capability of finding biomarkers: water, ozone and evidence of photosynthesis. If free oxygen is detected, life may not be far behind. Future discoveries may also be achieved by a NASA/JPL plan to block out bright starlight with a remote object, allowing a space-based telescope to see a planet. 

     Kasting is working to advance this technology as chair of the Terrestrial Planet Finder Coronagraph Mission Definition Team. The concept is also being developed by the New Worlds Mission, headed by Webster Cash, professor of astrophysics at the University of Colorado.

     A final detection method to gauge a planet’s composition is measuring planet shine, where photons from a moon can be used to calculate a planet’s composition. ■