Recap Extraterrestrial Life

1
Recap Extra-terrestrial Life

• Give 4 characteristics of life.
• What are the extremophiles ?
• What is the habitable zone ?
• Where could life exist in our solar system ?

2
Extra-terrestrial Life (II)

• Extra-Solar Planets
• SETI and Drakes Equation
• Extra-terrestrial Life
• Colonizing the Universe

3
Introduction

• SETI- Search for Extra-Terrestrial Intelligence,
  a project launched by the late Carl Sagan.
• Drakes Equation quantifies the chances of
  success for SETI.

4
Extra-Solar Planets

• In the recent years over 100 extra-solar planets
  have been detected. The nearest are about 40
  light-years away.
• They cannot be seen directly with the current
  telescopes because their light (actually the star
  light that they reflect) is outshone by the stars
  they orbit.
• Direct measurements might become possible in the
  near future.
• Indirect observations include
• Astrometrics (deviations from the normal
  movement)
• Wobbling around the path detection
• Red-shift measurements
• Transit photometry (planet passes in front of the
  star)
• Star corona studies

5
Life in the Solar System (I)
As the mass of the star increases the habitable
zone moves further from the star.
6
SETI

• SETI has been emitting radio messages out
  into the Universe for decades in the hope of
  communicating with extra-terrestrial
  intelligence. The absence of responses make us
  wonder about the chances of success.

Arecibo
7
SETI Details

• What communication wavelengths ?
• What language to communicate ?

8
Drakes Equation

• Drakes equation determines the number of
  civilizations in the galaxy which might be
  capable of insterstellar radio communication. The
  equation is
• NRfpneflfifcL, where
• R is the average rate of star formation,
• fp is the fraction of stars with planetary
  systems,
• ne is the number of planets that have
  environments suitable for life,
• fl is the fraction of planets that have life,
• fi is the fraction that have intelligent life (on
  Earth it took millions of years of evolution and
  it created one out of a billion of species),
• fc is the fraction that developed the technology
• L is the average lifetime of a technological
  civilization.

9
Intelligent Life

• Defining intelligence is a difficult task.
  Dolphins, horses and even insects
  possess some degree of
  intelligence.
• But only humans acquire and apply
  knowledge, have fore and hindsight to
  imagine the future and to reflect upon the past.
• Intelligence evolved because it was favored by
  natural selection. It took millions of years to
  create one intelligent specie out of a billion
  and that makes some biologists (like G.Clayford
  of Harvard) say that the repeat in other planets
  is very improbable.

10
Conclusions on ET Life

• SETI has to wait for a long time because the
  nearest extra-solar planets are more than 40
  light-years away.
• The chances of intelligent ET life in our galaxy
  are probably good but we do not have the value of
  Drakes N. I.Asimov speculated in one of his
  books that N is around 300.
• Hard to speculate on how ET life looks like. We
  can say that the X-Files greys come from a
  small planet because of their fragile appearance.
  
• Apart from frequent and dubious claims (such as
  UFOs photos) until about 5 years ago there was
  little if any evidence that ET life exists.
• We do know that the chances of finding primitive
  forms of life in our solar system are good. Our
  bacteria survived on the Moon, and we may have
  traces of decomposed bacteria from Mars in some
  meteorites, but so far we found no live bacteria
  on Mars.

11
Colonizing our planetary system (I)

• Even if we find no life out there, we could
  colonize the Universe, or at least our galaxy.
• Our Moon was already visited, but it does not
  contain the elements and the chemicals to sustain
  life. If a colony is setup on our Moon it would
  be completely dependent on Earth supplies.
  
• Mars, on the other hand, has all the
  elements to build a colony
  and bred plants.

12
Colonizing our planetary system (II)

• Many scientists favor the colonization of some
  asteroids, such as Ceres which has a diameter of
  967 km (half of Pluto). These asteroids can be
  mined for valuable metals and chemicals.
• The NASA animation on the right shows a
  probe orbiting Eros, the second largest asteroid.
• The colonization needs solutions to the
  physiological effects of
  zero-gravity, or the creation of
  artificial
  gravity. Mars is much
  better in that sense, as it
  has
  38 of the Earth gravity.

13
Colonizing our planetary system (III)

• Terraformation is the science of making another
  planet/asteroid habitable.
• For Mars it would imply increasing the
  atmospheric pressure by 200 times (to be thicker
  than our due to its lower gravity) and the
  temperature by 60 degrees. NASA concluded that
  this is not only feasible but also plausible.
• Venus is the only other candidate. But with its
  482 degrees at the surface and an atmosphere 92
  times thicker than Earth, this task will be much
  more difficult than with Mars.
• Jupiter is a gas giant type planet (no surface
  for life to grow on), but its moons (such as
  Europa) are interesting candidates for
  terraformation.

14
Colonizing our galaxy (I)

• More than 100 Jupiter-type planets were already
  observed in other stellar systems.
• While our Jupiter (and its moons) are too far
  from the Sun, other Jupiter-type planets and
  their moons could be in the habitable zone.
• There are already signs that some of the observed
  planets travel through habitable zones at least
  part of their orbits (one can determine the
  proximity to the star by measuring the revolution
  time).

15
Colonizing our galaxy (II)

• Colonizing the solar system and the nearest
  stellar systems is relatively easy to visualize,
  but how about our galaxy ?
• In our galaxy there are about 200 billion stars
  and if one travels at about 25 of the speed of
  light it would take about 300,000 years to go
  across the galaxy. Can it be done ?
• According to Einsteins relativity, if one
  travels at close to the speed of light time will
  slow down for the traveler
• Today the travel speeds are very low. New
  technologies are needed to speed up the
  inter-stellar travel.
• Nuclear fusion with helium-3 isotopes could power
  the spaceships. For instance our Moon and Uranus
  have large quantities of helium-3.
• The colonization could be done through small
  jumps (of a few light-years), which would then
  self-replicate ships using local sources of
  helium-3.

16
Colonizing other galaxies

• Today this is hard to imagine because it involves
  flights over distances of millions of
  light-years.
• Science fiction invented the warp speed, ie the
  creation of mini black holes used for space-time
  travel.
• Theoretically this is possible but technically
  far from our capabilities.