After a busy day at
work, you emerge from the office into a fading March evening of 2029. Taking
the usual route home, you check your phone for the first time in hours and discover
12 new messages. The first one simply says “Have you heard?!”. Your heart rate quickens.
What could this exciting news be? Fumbling for the next message you quickly
skim the text… In a state of shock, the phone drops from your hand. This is the moment you, like the
rest of humanity, learn of the most important scientific discovery in centuries: that life
exists elsewhere in the universe.
Although this vision of the future may seem speculative, the
technology to detect life on planets around other stars already exists. All
that is lacking is the enthusiasm of the general public and the financial
backing of the world’s governments.
The 20th century was a truly optimistic time for
those looking for life elsewhere in the universe. The early part of the century
saw huge public intrigue over possible canals on Mars. However, by the time the
Viking probes arrived in the 1960s, Mars was known to be a cold and desolate
place. More recent rovers have confirmed that if Mars was ever habitable, it
has not been so for billions of years. Missions to Jupiter and Saturn have also
captivated public attention, with moons such as Europa and Titan being hyped to
as possible havens for life. While the presence or lack of alien life in the
solar system has not been settled, no environment has been found as comfortable
for life as Earth’s surface.
However, in 1995 astronomers discovered the first solar
system outside of our own. While this first ‘extra-solar’ planet was far from supportive
to life, it marked the beginning of a new age of discovery for science. To date
more than 750 exoplanets have been confirmed, and NASA spacecraft Kepler has
found more than 2321 candidates including numerous Earth-sized planets. The
Gaia mission, launching next year, could also potentially discover tens of
thousands more. This revolution is space sciences mean there are now thousands
more places to look for life in the universe, and missions have already been
proposed to do just that.
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| The Darwin mission, with 6 space telescopes. |
Since the early 00s both NASA in America and ESA in Europe
hatched similar plans to fly an array of planet-hunting space telescopes high
above the Earth. NASA’s Terrestrial Planet Finder, or TPF-I, and ESA’s Darwin mission
comprised of between three and six 1.5m telescopes collecting infra-red light
from a target star system. The telescopes would fly in a precise formation,
allowing the light detected from each dish to be digitally combined. Not only
does this processing give an effective telescope diameter of 100m, it also
enables the light from the parent star in this system to be removed. This is
called interferometry and is frequently used on ground-based telescopes
including the Very Large Telescope array in Chile. Unlike in Chile, however, the
distorting effects of Earth’s atmosphere are removed, and this array of space
telescopes would be able to directly observe and characterise Earth-like
planets.
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| The spectra of Mars, Earth and Venus. Only Earth, with H2O, CO2 and O3 is habitable |
By measuring the light coming from such a planet across a
variety of wavelengths, the TPF-I or Darwin missions could take spectra of any Earth-like planet discovered. These infra-red spectra could probe their atmosphere, and can tell if such a planet is inhabited. Life as we
know it produces a distinctively imbalanced atmosphere. On Earth large amounts
of oxygen coexist with methane, ozone, carbon dioxide and water; a mix that without life’s unique
processes could not exist for long. “I would be 99% sure that life was present
if I saw this combination of planetary characteristics” says Professor James
Kasting, writer of the book How to Find a Habitable Planet.
These missions were capable of putting to rest one of the
biggest questions ever asked by a conscious mind: ‘Are we alone in the
universe?’ Geoffrey Marcy, exoplanet pioneer, said “I think TPF is our Human Genome
Project”. What happened to TPF and Darwin, I hear you ask. In 2007 Darwin were indefinitely shelved, and in 2011 Terrestrial Planet Finder was cancelled completely. In total both projects wasted more than 10 years planning
and many millions of dollars of funding with no end result.
One of the main factors blocking the development of such an
Earth-finding mission is cost. Such a project could plausibly run to tens of
billions of pounds. While this figure dwarves the biggest science experiment
ever made, the Large Hadron Collider at CERN (a mere $9bn), it pales in
comparison to other projects, such as war in Afghanistan ($120bn a year) and
global tax evasion ($3100bn!). Just like the LHC, this cost could be spread
between European states and the US, and even new space-faring nations such as
India and China. For a project that might answer fundamental questions about our
universe and captivate people across the planet, a few billion pounds really doesn’t
seem that much to ask.
James Kasting believes that, without the interference of
politics, such a concept could be designed, built and flown into space within
15 years. And the only way to get such plans onto the table is to tell the
politicians and policy-makers of the world that this matters to us. This groundswell
of public interest in exoplanets & astrobiology could mean that on one evening
in 2029 you discover that our Earthly biology has done the
unthinkable; discovered life on another world.
