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Look Down
WHERE WOULD ASTRONOMY BE WITHOUT LIGHT? Save for a few
rocks that have crashed to Earth or that we’ve managed to bring
back from the closest bodies to us, most of what we’ve learned
about the cosmos has come courtesy of electromagnetic radiation
arriving from afar. Visible light, X-rays and gamma rays, ultraviolet
and infrared radiation, microwaves and radio waves — all these forms of light
have collectively enabled us to penetrate some of our universe’s deepest secrets.
See, for example, “Spitzer’s Legacy” on page 18.
Yet, ironically, astrobiologists are itching to go where there’s no light at all.
The reason is to potentially answer one of the biggest cosmological questions of
all: Does life exist elsewhere?
Many scientists would agree that one of the most likely places to fi nd signs
of extraterrestrial life is where darkness reigns — namely, belowground. If living
things do exist beyond our planet, lightless zones such as the Martian subsurface
or the deep oceans sheltered beneath the icy crusts
of Europa and Enceladus might well harbor it.
As Javier Barbuzano writes in our cover story on
page 34, we’ve known for decades that life on Earth
can survive in total darkness. Entire ecosystems
thrive in the ocean depths thousands of feet below
the point where the last feeble rays of sunlight can
reach. Similarly, microorganisms have been found
doing just fi ne more than a mile underground.
In these stygian realms, photosynthesis, the
basis of all life on the surface, is impossible.
Instead, microbes at the base of the food chain have resorted to chemosynthesis,
gaining their energy from chemical reactions. In some cases, this has allowed a
menagerie of much larger organisms to exist, such as the giant tubeworms that
cluster around hydrothermal vents on the seafl oor.
Some scientists suspect that life on our planet might well have gotten its
start in such sunless environs, rather than on the surface in, say, Darwin’s
“warm little pond.” Maybe it began in a similar fashion on other bodies in our
solar system and fl ourishes there to this day, awaiting our probes.
Just think: Light allows us to investigate objects and events right across the
universe. Yet in all that inconceivably vast space, the spot where we’re most
likely to turn up evidence of other life forms is perhaps but a few tens of feet
below the surface of our nearest neighbors. It’s like pondering where on our
enormous globe you might strike gold, when the most
promising spot is right where you’re standing.
NASA and other space agencies: Here’s to going down.Editor in ChiefThe Essential Guide to Astronomy
Founded in 1941 by Charles A. Federer, Jr.
and Helen Spence Federer
EDITORIAL
Editor in Chief Peter Tyson
Senior Editors J. Kelly Beatty, Alan M. MacRobert
Science Editor Camille M. Carlisle
News Editor Monica Young
Associate Editor Sean Walker
Observing Editor Diana Hannikainen
Senior Contributing Editors
Dennis di Cicco, Robert Naeye, Roger W. Sinnott
Contributing Editors
Howard Banich, Jim Bell, Trudy Bell, John E. Bortle,
Greg Bryant, Thomas A. Dobbins, Alan Dyer,
Tom Field, Tony Flanders, Ted Forte, Sue French,
Steve Gottlieb, David Grinspoon, Shannon Hall,
Ken Hewitt-White, Johnny Horne, Bob King,
Emily Lakdawalla, Rod Mollise, James Mullaney,
Donald W. Olson, Jerry Oltion, Joe Rao, Dean Regas,
Fred Schaaf, Govert Schilling, William Sheehan,
Mike Simmons, Mathew Wedel, Alan Whitman,
Charles A. WoodContributing Photographers
P. K. Chen, Akira Fujii, Robert Gendler,
Babak Tafreshi
ART, DESIGN & DIGITAL
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AMERICAN ASTRONOMICAL
SOCIETY
Executive Offi cer / CEO, AAS Sky Publishing, LLC
Kevin B. Marvel
President Megan Donahue, Michigan State University
President Elect Paula Szkody, University of Washington
Senior Vice-President Michael Strauss, Princeton
University
Second Vice-President Joan Schmelz, Universities
Space Research Association
Third Vice-President Geoffrey C. Clayton, Louisiana
State University
Treasurer Nancy D. Morrison, University of Toledo (ret.)
Secretary Alice K. B. Monet, U.S. Naval Observatory (ret.)4 JANUARY 2020 • SKY & TELESCOPE
NASAJust scratching the surface:
a 2-inch-deep hole drilled by
the Curiosity Rover on Mars