18. • Ever since people have started observing the sky, there
has been the question of whether we are alone or not.
• Frank Drake, the scientist who invented the Drake
equation which is an equation to find the number of
civilizations in our galaxy, estimates that there are
10,000 communicating civilizations in our galaxy
• Nasa estimated in 1999 that there were 125 billion
galaxies in our universe.
19. Very conservative estimates say that there are
approximately 6.25 billion life supporting solar
systems in the universe.
It is very probable that there is a least one planet out
there that is currently supporting life.
20. This diagram shows where planets could be in relation
to where the star is and size of the star in order to
support Earth-like life.
21. It’s possible that there were large oceans on Venus’s
surface 4 billion years ago, when the sun wasn’t as
Some scientists believe that early life forms were
blasted off the surface of Venus by meteor impacts and
managed to land on Earth, and start life on Earth.
There may still be small microbes living in Venus’s
atmosphere, 31 miles above the surface.
22. Long thought to contain life.
Many believe that water existed on Mars in the past,
and there may still be water below the surface.
A test by a Mars rover in 2008 showed that there was
water in the soil.
There is evidence that water flowed on the surface
within the past 10 years.
23. • Despite the fact that Jupiter is a gas planet, many
people believe that there could be life on it.
• Some people believe that there are fish type creatures
that live on Jupiter in the atmosphere, but the
atmosphere is very intense and would likely kill any
• Microbes would have to go very far into Jupiter to find
an area where water doesn’t freeze, but the pressure
would be very intense.
24. There are 138 known moons in our solar system
and several of them appear to be capable of
Europa is one of Jupiter’s moons. It’s possible that
below the ice there is water that is heated by vents,
supporting plant life.
25. • Enceladus is one of Saturn’s moons and is thought to
be able to support life. There is strong evidence
supporting the theory that there is a large salt ocean
below the surface, possibly supporting life.
• Titan, Saturn’s largest moon, has lakes of liquid
methane on the surface and a heavy atmosphere. This
is the first body outside of Earth known to have surface
27. •It is more than likely that there is life outside of our
solar system that exists, but we haven’t discovered.
•Scientists send out radio signals in space hoping to
get a response from aliens, but this would be highly
unlikely, because if another civilization was using
radio technology now, by the time it gets there they
might have moved on, or not even discovered it yet.
•Scientists are looking in distant solar systems for
planets that are a certain distance from the sun and
have the right planetary conditions to support life.
28. On April 24, 2007 scientists discovered an extra solar
planet, a planet that’s not in our solar system, that
orbits the right distance from it’s star to support life.
The planet was named Gliese 581 c, and was at first
thought to have liquid on the surface. Recent research
has found that there could be an atmosphere with lots
of greenhouses that would cause high temperatures,
lessening the chance of discovering life on the planet.
29. Scientists are now looking at Gliese 581 d which is also
inside the habitable zone. It is approximately 20 light
years away in the constellation Libra.
So far, scientists have discovered over 400 extrasolar
planets, and scientists are discovering even more every
month increasing the chance that we will make
contact with alien life soon.