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What is an extraterrestrial?
Are we alone in the universe?
Life beyond Earth, or “extraterrestrial
life,” is certainly a possibility in the minds and
imaginations of NASA astrobiologists. In fact, “to
find life beyond”, and “to explore the universe
in search of life” are key components in NASA’s
Vision and Mission statements.
How is life defined? As we know it, all living
things have certain needs. They use energy, take in materials,
get rid of waste, somehow respond to their environment,
reproduce, and grow and change.
Perhaps less might be needed for other forms
of life.
According to astrobiologists, liquid water
is a must for all life as we know it. Carbon is a close
second. Carbon atoms can form bonds that become organic
molecules, the “stuff” of Earth-based life.
Other atoms—such as hydrogen, oxygen, nitrogen, and
sulfur—are also helpful when looking for life.
Find these materials on a planet with one
of the billions of sun-like stars in our Galaxy, and you
may find something living.
That’s not as far-fetched as you might
think. Even within our Solar System we find a few “contenders”
for life.
Astrobiologists believe that Mars once had
surface water and may still have underground bodies of water.
From uncrewed missions, it’s clear that frozen water
is found within the crust of the Martian surface. Martian
meteorites even tease scientists with what appears to be
fossilized bacterial life, though most now doubt that possibility.
Europa, one of Jupiter’s moons, has
some merit for life forms, too. Icy streaks and cracks fracture
Europa’s surface. On closer inspection, these streaks
are evidence of circulating water beneath an icy surface.
Could something be living in that water?
It seems natural to ask these questions and
wonder. Some of us do more than wonder by sending out signals,
hoping to hear answers. SETI (Search for Extraterrestrial
Intelligence) astronomers send and listen for radio transmissions
from distant civilizations. These astronomers are intentionally
broadcasting signals through radio telescopes. Radio waves
are well suited for this job. They travel great distances,
unaffected by gas and dust.
Since the first radio transmission, Earth’s
radio and television broadcasts fill the space around the
solar system within 100 light years in all directions. Imagine
what impression we might be making as extraterrestrials
eavesdrop on bits and pieces of our radio and television
chatter.
Other messages have also been sent into space.
Pioneers 10 and 11, launched in 1972 and 1973, both carried
small metal plaques identifying their time and place of
origin for the benefit of any other spacefarers that might
find them. The two Voyager spacecrafts, launched in 1977,
each carry a plaque and phonograph record with human voices.
They reach out to whoever or whatever might cross their
path. Considering the size of space, the odds are small.
Yet the chance was worth the effort.
Are we alone in the universe?
Perhaps not alone. But most astrobiologists
believe that any life found, at least here in our own solar
system, is likely to be much simpler than imagined human-like
life forms. Still, the possibilities are mind boggling.
The NASA Vision
To improve life here,
To extend life to there,
To find life beyond.
The NASA Mission
To understand and protect our home planet,
To explore the universe and search for life,
To inspire the next generation of explorers as only NASA
can.
Visit the links below for more resources from
NASA:
Yikes,
A Space Creature! - To design an animal that
can adapt to live in a space environment.
It's
Alive! - To conduct a simulated experiment
with soil samples to look for signs of life in soil.
Out
of This World Work Stations - To create a workstation
that accommodates the unique characteristics of an extraterrestrial
life form.
Discovering
New Worlds - Read how NASA is trying to answer
the age old question, "Are we alone in the Universe?"
This article also features multimedia links and related
sites.
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