Astronomy unit 7

What is astrobiology

Study of life in the universe

What do astrobiologists try to find out

What conditions are needed for life and where those conditions might be found in space

What characteristics does all life on earth share

Cells, uses energy (metabolism), homeostasis, grows and develops, responds to environment, reproduces, passes on traits to offspring (heredity)

What are all living things made up of

Cells

What are cells

Tiny “building blocks” that carry out life’s functions

Organisms that are known for having one cell

bacteria

How many cells do humans have

Trillions

What is metabolism

Process of taking in food or chemicals and turning them into energy

What is homeostasis

Living things maintain stable internal conditions even when their environment changes

Why is homeostasis essential for survival

Cells can’t function properly if conditions swing wildly

What is heredity

Living things pass down traits through genetic material (DNA)

What does conditions for life refer to

Set of environmental, chemical, and physical factors that allow living organisms to survive, reproduce, and evolve

What are some conditions for life

Essential elements, organic molecules, water, temperature, pressure, energy sources

What elements is life on Earth based on

Carbon, hydrogen, nitrogen, phosphorus, and sulfur

What organic/Complex molecules form

The basis of biological structures

Examples of organic/Complex molecules that form the basis of biological structures

Amino acids, nucleic acids, and lipids

What does water do

Facilitates chemical reactions, transports nutrients, and helps maintain cell structure

What does life typically require to maintain biochemical reactions

Moderate temperature range

What pressures can affect the state of water and cellular functions

Atmospheric and hydrostatic

What are critical for driving metabolic processes as energy sources

Photosynthesis and chemosynthesis

Why is liquid water important especially regarding astrobiology

Dissolves a wide range of substances, allows chemical reactions necessary for life, regarded as necessary for life as all the life we know uses it

What is the habitable/goldilocks zone

Region around a star where temperatures allow liquid water to exist on a planet’s surface

What influences the amount and type of radiation a planet recieves

Size, temperature, and activity of the host star

What do stable orbits within the habitable zone ensure

Consistent environmental conditions necessary for life

What are extremophiles

Organisms that thrive in environmental conditions considered extreme or inhospitable to most forms of life

What are the characteristics of extremophiles

Adaptations that allow them to survive high or low temperatures, extreme pH levels, high salinity, intense radiation, or crushing pressures

What is the importance of extremophiles

Challenges our understanding of the limits of life

What are thermophiles

Extremophiles that thrive at high temperatures

What are psychrophiles

Extremophiles that thrive at very low temperatures

What are acidophiles

Extremophiles that live in highly acidic environments

What are alkaliphiles

Extremophiles that prefer very alkaline (basic) conditions

What are halophiles

Extremophiles adapted to very high salt concentrations

What are barzophiles (piezophiles)

Extremophiles that thrive under high pressure

What are radioresistant organisms

Extremophiles that can survive high levels of ionizing radiation

Potential habitats of extremophiles

Mars, Europa and Enceladus

Why might mars be a home to extremophiles

Microbial life could exist in acidic soils and the cold environment

Why might Europa and Enceladus be homes to extremophiles

Subsurface oceans beneath icy crusts could support life similar to thermophiles or psychrophiles

What are tardigrades

Microscopic animals all around Earth that survive in extreme conditions and enter cryptobiosis until conditions improve

What is cryptobiosis

Shutting down metabolism almost completely

What is a biosignature

Thing that is evidence of past or present life

What is the main key of being a biosignature

Something that’s difficult or impossible to produce without life

In what forms can biosignatures be in

Chemical, physical, biological

What are atmospheric biosignatures

Atmosphere altered by the life on the planet

Why is oxygen considered reactive

Shouldn’t exist in large amounts without constant replenishment

How is oxygen created on Earth

Photosynthetic organisms like planets and algae

Why is oxygen not a definitive proof of life

Can be produced by non-biological processes like chemical reactions and photolysis

Biological means of producing methane

Bacteria, decomposition, digestive systems

Non-biological ways of producing methane

Volcanic activity, geological processes

What type of chemical on Earth is 90% biologically produced

Methane

Why must methane be constantly replenished

It breaks down easily

Why is finding oxygen and mathane together especially interesting

They react together

Why might there be life on Venus

Could be phosphine in its atmosphere which isn’t known to have a non-biological way of being produced

What are organic molecules

Building blocks of life (RNA/DNA, amino acids, lipids)

How to identify chemical biosignatures in organic molecules

Specific chemical arrangements life prefers, complexity that’s hard to explain without biology

Most common physical biosignatures

Fossils, stromatolites (structures built by bacteria)

What is the challenge of identifying physical biosignatures

Very hard to confirm without close examination

What are some surface biosignatures

Pigments produced by organisms, certain plants reflect red light in a certain way, seasonal changes in surface color or chemistry, geometric patterns that suggest intelligence

What makes a good biosignatures

Detectable from far away, hard to produce without life, producible by a wide range of life

What is an exoplanet

A planet that orbits a star other than our sun

Why are exoplanets hard to identify

Stars are bright but planets are dark, we need indirect methods of viewing them

Ways we’ve developed to find exoplanets

Transit method, radial velocity/doppler, direct imaging, gravitational microlensing, astrometry

What is the transit method

Watching to see if a planet goes over a star over time in a mini-eclipse

What is a light curve

Graph of a star’s brightness over time

What do we learn from light curves

Planet size, orbital period, orbital distance, atmospheric composition

What are the limitations to the transit method

Planet’s orbit must be aligned with our view, only 1% of planets have the right alignment, hard to detect

Popular telescope that used the transit method and revolutionized our understanding of how common certain planets are

Kepler space telescope

What is the transiting exoplanet survey telescope (TESS) known for

Surveys nearly the entire sky (much larger area than Kepler), has discovered thousands of exoplanet candidates, 720 confirmed

What we learn from radial velocity method

Bigger wobbles mean the planet is larger, the orbital period by how long it takes for a wobble pattern to repeat

Limitations of the radial velocity method

Works best for massive planets that have bigger wobbles, requires very precise measurements, harder when planets are further away from their stars since wobbles are slower

How are the transit method and radial velocity methods combined

Transit tells us size, radial tells us mass, together density is calculated, density tells us what type of planet

What is direct imaging

Actually taking a picture of the exoplanet, extremely difficult because stars are so much brighter than planets

Types of exoplanets

Terrestrials, super earths, neptunian, gas giants

What are terrestrial exoplanet like

Similar to our planet and planets near us, made primarily of rock and metal, most likely to be habitable if in the right zone, harder to detect because they’re smaller

What are super Earth exoplanet like

Larger than Earth but smaller than Neptune, may be terrestrials, none in our solar system, most common exoplanet discovered

What are gas giant exoplanets like

Similar to Jupiter and Saturn, made mostly of hydrogen and helium, usually too large and gaseous for life as we know it, moons might be habitable

What are hot Jupiter gas giants like

Gas giants very close to their stars, orbital periods of just days, none in our solar system, shouldn’t exist according to solar system formation theories, likely formed farther out and migrated inward

What are neptunian exoplanets like

Similar to Neptune and Uranus, made of water methane and ammonia ices, rocky core, thick hydrogen/helium atmospheres, some might have liquid water deep in their atmospheres

what is the TRAPPIST-1 system

Seven earth-sized planets around a small cool star, three or four planets in the habitable zone, 39 light years away, all seven planets are close to their star (all would fit inside mercury’s orbit)