AST - Search for Life in the Universe

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Astrobiology

The scientific study of life int he universe, including how life began, how it evolved, where it might exist, and whether life exists beyond earth

Extraterrestrial

Originating outside of Earth. Extraterrestrial life means life that originated somewhere other than Earth.

Why Earth Matters

Earth is our only confirmed example of life, so scientists use Earth life as a starting point when thinking about life elsewhere.

Liquid Water

All known life requires liquid water. However finding liquid water by itself doesn't prove that life exists.

Places scientists consider

Potential environments include Mats, Europa, Enceladus, and Titan. Scientists look for environments that would provide conditions suitable for life.

Evidence vs Speculation

Scientists distinguish what is known, what is possible, and what has actually been supported by evidence.

Interdisciplinary Science

Astrobiology draws on astronomy, planetary science, biology, chemistry, geology, and physics

Geocentric Model

Earth-Centered Model

Heliocentric Model

Sun-centered model of the Solar System

Copernican Principle

The general idea that Earth does not occupy a special or central position in the universe

Hypothesis

A proposed explanation that can be tested

Scientific Theory

A well-supported explanation that has survived extensive testing. A scientific theory is not a simple guess.

How science works

Scientists make observations, ask questions, develop hypotheses, make predictions, test them, analyze evidence, and revise explanations when needed.

Self-Correcting science

When new evidence conflicts with an existing explanation, scientists can modify or replace that explanation

Universe

Everything that exists, including space, time, matter, and energy

Galaxy

A huge collection of stars, gas, dust, and other materials held together by gravity

Cosmic hierarchy

Earth → Solar System → Milky Way Galaxy → Universe

Light-Year

A unit of distance equal to the distance light travels in one year. It is not a unit of time. Looking at distant objects also means looking into the past.

Big Bang Theory

The leading scientific explanation that the universe began in an extremely hot, dense, state and has been expanding.

Redshift

A shift. of light toward longer, redder wavelengths. The redshifts of distant galaxies are important evidence for an expanding universe.

Atoms

Atoms contain protons (positive), neutrons (no charge), and electrons (negative). Atomic number equals the number of protons.

Important elements for life

Hydrogen, Carbon, Nitrogen, and oxygen are especially important. Carbon can form many complex molecules.

Planets in order

Mercury → Venus → Earth → Mars → Jupiter → Saturn → Uranus → Neptune

Terrestrial Planets

Mercury, Venus, Earth, and Mars. They are rocky and relatively small.

Jovian planets

Jupiter, Saturn, Uranus, and Neptune. They are much larger and rich in gases and other volatiles.

Nebular Theory

A model for the solar system formation: a cloud of gas and dust collapsed under gravity, flattened into a rotating disk, and formed the Sun at the center and planets from material in the disk.

Mass

the amount of matter in an object

Weight

the force that acts upon an object

Speed

the rate at which an object moves

Velocity

speed and direction

Acceleration

change in velocity; acceleration has direction

Momentum

mass x velocity. Net force changes momentum which means there is acceleration.

Angular Momentum

Rotational momentum of a spinning or orbiting object is known as angular momentum. Formula: mass x velocity x radius

What did Newton discover?

• Three laws of motion

• Universal law of gravitation

• Newtons first law

Newton’s First Law of Motion

An object moves at constant velocity unless a net force acts to change its speed or direction.

Newton’s Second Law of Motion

An object’s acceleration depends on the net force acting upon it and the object’s mass, expressed by the formula F=ma

Newton’s Third Law of Motion

For ever force, there is always an equal and opposite reaction force. When you kick, (exert force on) a box, the box kicks you back with equal and opposite reaction force (so it hurts you)

Conservation of Energy

Energy can change form. But the total energy has to be conserved.

What determines the strength of gravity?

• the universal Law of Gravitation

1) Every mass attracts every other mass

2) Attraction is directly proportional to the product of their masses

3) Attraction is inversely proportional to the square of the distance between their centers

Oumuamua

the first interstellar asteroid from outside the solar system, taking a hyperbolic trajectory around the Sun

Atomic Number

number of protons in the nucleus

Atomic Mass Number

number of protons + neutrons

Atomic Energy Levels

each element has its one set of fixed electron orbits, and each orbit has its now energy level.

Organic Molecules

(involve carbon) Among all elements carbon is almost unique for its ability to form a variety of chemical bonds with its 4 valence electrons.

Ionic Bonds

electron from one atom goes to another, opposites attract

Covalent Bonds

electrons shared between atoms. Negatively charged electrons are positively charged nuclei

Hydrogen Bond

negatively charged and positively charged sides attract each other

Evaporization and Water Vapor

water molecules are moving around in liquid water due to hear, they are pulling each other by hydrogen bonds to stay in the water.

Activation Energy

• we need to initiate chemical reactions, for example, by external ignition.

• In the end, you get energy through the chemical reactions, but you have to first put energy o start the reaction

Adenosine Triphosphate (ATP)

• currency of intercellular energy transfer

• Store energy as the binding energy of the green part

Equilibrium

balance

Disequilibrium

unbalanced

Atoms

made of nuclei and electrons

Isotopes

same number of protons different number of electrons.

Nuclear Fission

big nucleus splits into smaller pieces

Nuclear Fusion

small nuclei stick together to make a bigger one

Wavelength

the distance between two wave peaks

Frequency

the number of times per second that a wave vibrates up and down

Red light

longer wavelength = lower frequency = lower energy

Blue light

shorter wavelength = higher frequency = higher energy

Energy Level transition

electrons in atoms can take only the orbits of particular energies specific to the element, each element has its one set of orbits

If we represent the solar system on a scale that allows you to walk from Sun to Pluto in a few minutes

Planets are about the size of a ballpoint and the nearest stars are thousands of miles away

How many of the planets orbit around the Sun in roughly the same direction as Earth?

ALL

Solar Nebula

1) Starting from a cloud of gas in interstellar space

2) Some part of the cloud collapse by their own gravity. The piece that became our solar system, the solar nebula

3) At its start, the solar nebula was probably a few light-years in diameter (about twice the diameter of Pluto’s orbit)

Three Processes During the Collapse

1) Heating

2) Spinning

3)Collisions

Heating during the collapse

The Conservation of EnergyL the collapse CONVERTS gravitational potential energy into thermal energy (heat)

Gas particles crashed into one another, converting energy of infilling motion into random motions of thermal energy

The solar nebula became the hottest at the center where much the mass collected to form the protosun

The protosun eventually became so hot that fusion ignited at its core - t which the sun became a full-fledged star

Spinning

The conservation of angular momentum: the solar nebula rotated faster and faster as it shrank in radius

The spinning helped ensure that NOT ALL of the material of the solar nebula collapsed onto the protosun

The greater the angular momentum of a rotating cloud,

the more spread out it will be (spinning pizza dough)

Collisions

A cloud may start with any size or shape. Small clumps in the cloud may be moving in random directions with random speeds. As the cloud collapses these clumps collide and merge, killing the random motions and averaging the old speeds. Random motions in the cloud become more orderly, as the cloud collapses, challenging the cloud’s shape into a rotating, flattened disk.

Reduces their ellipticies, making the orbits more circular.

Flattening is a natural consequence of collision

Why are the observed motions in the solar system generally so orderly?

• Flattening of the disk explains why all the planets orbit in nearly the same plane

• Spinning explains why planets orbit in the same direction, and also plays a role in making most of the planets rotate in the same direction.

• Collisions explains why most planets have nearly circular orbits.

• Explains the layout of our sola system

Why do the inner and outer planets divide so neatly into two classes?

Terrestrial: Planetesimals made of rocks and metals

Jovian: Planetesimals mainly made of ice flakes

Why are there a large number of asteroids and comets in two different regions?

These leftovers became asteroids and comets:

• inside the frost line - asteroids (planetesimals of rocks and metals)

• outside the first line - comets (icy planetesimals)

Evidence of nebular collapse

• the red glow in the center of each disk is a newly formed star.

• Dark silhouette around the star is a dusty protoplanetary star

Condensation

solid particles condense from gas in the flattened, rotating disk. This process depends primarily on temperature.

Frost Line

• temperature decreases with distance from the Sun

  • Inner regions = hot

  • Outer regions = cool

Hydrogen compounds

could condense only beyond the frost line which may lead between the current Asteroid Belt and Jupiter.

Which o the following is correct in the formation process of the Solar System?

Rocks can form close to the Sun but Ices cannot

Planetesimals

bodies that could or did come together with many others under gravitation to form a planet

• are made of rocks, metals, or ices, but there are more icy planetesimals outside the first line

• the planetesimals in the inner solar system could not grow very large, since rocks and metals made up 0.6% of the material

• Beyond the frost line, planetesimals could be built from ice flakes and grow much larger, since ice flakes were more abundant.

Plate Tectonics

the slow motion of the

Snowball Earth

deep ice ages where some if not all of Earth’s surface was covered in ice.

The three theories for the origin of the moon

1) Co-formation

2) Capture

3) Rotational split

all failed

Co-Formation theory

• earth and moon formed together

• problem: gross density differences between Earth and moon

Capture theory

• Earth captures a rogue Moon in the early solar system

• Problem: the moon would have to somehow lose significant energy to fall into orbiting Earth

Rotational Split theory

• early earth spins so fast moon breaks off

• problem: fails o explain the difference in densities

Composition of the Moon

• the low average density of the moon

  • about the same as the density of Earth’s mantle

• Luna rRocks

  • the overall composition similar to Earth’s mantles

  • virtually no volatiles material

The Giant Impact Model

a large Mars-sized planet, named Theia blasted mantle material which would latter accrete into the Moon.

• the moon is made from the Earth’s mantle

How does gravity cause tides?

• moon gravity pulls harder on near side of Earth than on far side (because the gravity is stronger at a shorter distance)

• difference in Moon’s gravitational pull stretches Earth

Size of Tides

depends on Moons location with respect to Sun and Earth

What helps to determine the phase of the moon?

the moons location with respect to Sun and Earth

Tidal Friction

• gradually slows Earth rotation and makes Moon get farther from Earth (3.8 cm per year)

• Moon once orbited faster (or slower); tidal friction caused it to “lock” in rotation synchronous to Earth rotation

Moons role in Earth’s long-term climate stability

the moons gravity exerts a stabilizing influence on the Earth’s axis tilt

Defining Life

Gerald F. Joyce Definition: “Life is self-sustained chemical system capable of undergoing Darwinian evolution” but he added “Life is self-sustained chemical system capable of evolving new functions and undergoing Darwinian evolution”

Six Key properties of life

1) order

2) reproduction

3) growth and development

4) energy utilization

5) response to environment

6) evolutionary adaptation

First Law of Thermodynamics

any kind of energy can be turned into any other kind of energy (the same as the conservation of energy)

Second Law of Thermodynamics

when let alone, the energy in a system undergoes conversions that lead to increasing disorder

Mechanism of Evolution: Darwin’s Logic

1) overproduction and competition for survival

2) Individual Variation

Artificial Selection

The breeding of plants and animals by humans over the past few thousand years.

Cells

the basic structure of life

• separated from one another via a membrane

• provide structure for life

• site of metabolic processes

• contain hereditary information (DNA)

Eukaryotes

have a nucleus