Chapter 9 Flashcards
(27 cards)
Astrobiology
The study of the origin, evolution, distribution, and future of life in the universe including extraterrestrial life and life on Earth.
Solar Habitable Zone
Hypothetical distance around a star that would support life as we know it.
Liquid water exists on a planet.
Can change over the lifetime of a star.
Galactic Habitable Zone
Too close to the center of the galaxy is dangerous due to supernovae and gamma ray bursts.
Too far out and there’s not enough heavier matter like carbon.
Liquids i the Solar System
Mars used to have a lot of liquid water and still has a little.
Europa, a moon of Jupiter, is also thought to contain liquid water.
Titan, a moon of Saturn, contains surface liquid methane and ethane.
Mars
Liquid water in past.
Possible liquid water now.
Thin atmosphere.
Surface unprotected from solar radiation.
Geologically dead.
Mars has disputed amounts of methane that can have a geological or biological origin.
Europa
Composed of rock.
Covered in ice, with possible liquid water underneath.
Has oxygen in its atmosphere.
Has strong tidal forces.
Titan
Dense atmosphere. Liquid on surface. Wind and rain. Its methane cycle is like our water cycle. Protected from solar wind by Saturn. Has complex organic molecules.
Panspermia
Hypothesis that life exists throughout the universe.
Life is dispersed by asteroids and meteors.
Interplanetary vs Interstellar
Interplanetary is between planets in a solar system.
Interstellar is between stars.
Interplanetary Transfer
A large object hits a planet and knocks rocks off into space.
Microorganisms can float off the earth and be carried by stellar winds.
Evidence for Interplanetary Transfer
Rocks from Mars and the Moon are on Earth.
Meteorites have been found on Mars and the Moon.
Computer simulations predict a large impact on Earth would eject debris as far as Saturn.
Life from Earth is on Mars.
Interstellar Transfer
Just like interplanetary but a lot longer.
Driven by solar winds and gravity.
Meteoric Travel
The insides of meteorites don’t get that hot.
Landing on a planet is easier than getting off a planet.
Desiccation
Drying out fragments DNA.
A space hazard.
Ultraviolet light
Fragments and damages DNA.
A space hazard.
Radiation
Fragments and damages DNA.
A space hazard.
Cosmic Rays
Fast moving particles fragment and damage DNA.
A space hazard.
Radiation and DNA
High frequency radiation or fast moving particles can knock electrons off of atoms.
Direct Route vs Indirect Route
Direct: Electrons can be stripped off DNA.
Indirect: Electrons can be removed form another molecule to create a free radical that then damages DNA.
Radiation
Can break the backbone causing single or double stranded breaks.
Radiation can break the hydrogen bonds between the bases.
Radiation can damage the bases and change them chemically.
Extremophiles
An organism that thrives in conditions that would kill most life on Earth.
Archea, bacteria, animals, insects, worms.
Waterbears
An 8 legged animal.
Can live without water for 10 years.
Can survive at extreme temperatures and pressures.
Can survive the vacuum of space.
Can survive 1000 times as much radiation as other animals.
Deinococcus Radiodurans
Most radiation resistant organism known.
Can survive toxic environments.
Can survive desiccation.
Doesn’t make spores.
Instead of hiding in a spore it can repair its DNA from fragments.
Has multiple copies of its genome to serve as templates.
DNA repair helps it survive desiccation.
Exaptation
When a trait that evolved for one function becomes useful for another.
Ex. Feathers evolved for heat regulation later became useful for sexual displays and still later became useful for flight.
