Which of the following are thought to be key requirements for a world to have life?

Select all that apply.
Responses

a liquid medium
a liquid medium
active volcanoes
active volcanoes
a source of energy to fuel metabolism
a source of energy to fuel metabolism
strong sunlight to power photosynthesis
strong sunlight to power photosynthesis
a thick atmosphere
a thick atmosphere
a source of molecules from which to build living cells

✅ Correct answers:
– **a liquid medium**
– **a source of energy to fuel metabolism**
– **a source of molecules from which to build living cells**

These three are considered the *key universal requirements* for life as we know it.
Active volcanoes, strong sunlight, and a thick atmosphere can *help* create or sustain life but are **not essential prerequisites**.
Which of the following are considered to be advantages of water as a liquid medium over other possible liquid mediums for life found in our solar system (particularly liquid ammonia, methane, or ethane)?

Select all that apply.
Responses

Water molecules have charge separation that allows the formation of chemical bonds that can’t be made by the other substances.
Water molecules have charge separation that allows the formation of chemical bonds that can’t be made by the other substances.
Water remains liquid at a higher temperature than the other substances.
Water remains liquid at a higher temperature than the other substances.
Water is the only one of these substances that floats when frozen.
Water is the only one of these substances that floats when frozen.
Water molecules are electrically neutral overall.
Water molecules are electrically neutral overall.
Water is the only one of these substances that contains oxygen.
✅ Correct answers:
– **Water molecules have charge separation that allows the formation of chemical bonds that can’t be made by the other substances.**
– **Water remains liquid at a higher temperature than the other substances.**
– **Water is the only one of these substances that floats when frozen.**

These traits make water uniquely suited for life: its **polarity** enables complex chemistry, its **wide liquid range** supports varied environments, and **ice’s lower density** allows aquatic ecosystems to persist beneath frozen surfaces.
Why is life on the surface of Venus considered to be highly unlikely?
Responses

Spacecraft that have landed on Venus have not detected any evidence of life there.
Spacecraft that have landed on Venus have not detected any evidence of life there.
The atmosphere is too thick.
The atmosphere is too thick.
It is too hot.
It is too hot.
There is no atmospheric oxygen.
There is no atmospheric oxygen.
There are too many active volcanoes.
✅ **Correct answer:**
– **It is too hot.**

The surface temperature on Venus (~470 °C / 880 °F) is hot enough to melt lead, making stable liquid water — and thus life as we know it — impossible.
Why is life in the atmospheres of the jovian planets (Jupiter, Saturn, Uranus, Neptune) considered to be unlikely?
Responses

These atmospheres have strong vertical winds.
These atmospheres have strong vertical winds.
Life cannot exist in clouds.
Life cannot exist in clouds.
The gravity of these planets is too strong.
The gravity of these planets is too strong.
There is no water in these atmospheres.
✅ **Correct answer:**
– **These atmospheres have strong vertical winds.**

While the upper cloud layers might have suitable temperatures and contain water or other compounds, the **powerful vertical winds** would carry any potential life forms into deeper, hotter, and more hostile layers — making long-term survival unlikely.
The chapter and the video describe several worlds that might potentially have life underground, including several moons of jovian planets and the dwarf planet Pluto. What do these worlds have in common that makes us think they could potentially have life?
Responses

heavily cratered surfaces
heavily cratered surfaces
active volcanoes
active volcanoes
thick atmospheres
thick atmospheres
spectrographic signatures of organic molecules on their surfaces
spectrographic signatures of organic molecules on their surfaces
evidence that they may have subsurface zones or oceans of liquid water

✅ **Correct answer:**
– **evidence that they may have subsurface zones or oceans of liquid water**

These worlds — like **Europa, Enceladus, Titan, and Pluto** — are thought to harbor **liquid water beneath their icy crusts**, kept warm by internal heat or tidal flexing, making them potential habitats for life.
e are searching for life that is at least somewhat similar to life on Earth, the most important criterion in identifying a potentially habitable world is ________.
Responses

the presence of an atmosphere
the presence of an atmosphere
the presence of surface or subsurface liquid water
the presence of surface or subsurface liquid water
the size of the world
the size of the world
the distance of the world from its star

✅ **Correct answer:**
– **the presence of surface or subsurface liquid water**

Liquid water is considered the **most crucial ingredient for life as we know it**, since it acts as a solvent and medium for the chemical reactions essential to biology.
Suppose you were genetically engineering plants that you hoped to grow in a greenhouse on one of Jupiter’s moons.
In this scenario, you would want to engineer these plants to have
, so that they
✅ **Answer:**
you would want to engineer these plants to have **a metabolism that does not rely on sunlight for energy**, so that they **could survive in the dim light or darkness of Jupiter’s distant moons**.

🌱 In other words, they’d need to use **chemical energy (chemosynthesis)** instead of **photosynthesis**, since sunlight there is far too weak to sustain normal plant growth.
ability to survuce low pressure, more rtapid metaboolism or larger leaf structure so that they collect more sunlkight, grow faster, taller or could survive if not enough air for greenhouse

✅ **Best answer:**
You would want to engineer these plants to have **larger leaf structures so that they collect more sunlight**, since sunlight is extremely weak that far from the Sun.

☀️ **Reason:** On Jupiter’s moons, light intensity is about **1/25th** of what Earth receives. Bigger leaves increase surface area for photosynthesis, helping the plants capture enough energy to survive.
Why is the fact that water remains liquid at higher temperature than most other liquids considered to be advantageous to life?
Responses

Higher temperatures increase air flow on a planetary surface.
Higher temperatures increase air flow on a planetary surface.
Higher temperatures are more comfortable.
Higher temperatures are more comfortable.
Higher temperatures generally mean faster chemical reactions.
Higher temperatures generally mean faster chemical reactions.
Higher temperatures allow stronger chemical bonds.
✅ **Correct answer:**
– **Higher temperatures generally mean faster chemical reactions.**

This is advantageous because faster reactions can support more active metabolism and complex biochemistry — key factors for sustaining life.
oes Venus have any place where we may find liquid water today?
Responses

No
No
Yes, near active volcanoes that can provide heat
Yes, near active volcanoes that can provide heat
Yes, in high-altitude clouds
Yes, in high-altitude clouds
Yes, underground where the temperatures are cool enough for liquid water

✅ **Correct answer:**
– **Yes, in high-altitude clouds**

While Venus’s surface is far too hot for liquid water, **temperatures and pressures in the upper atmosphere** (around 50–60 km altitude) are mild enough that **droplets of liquid water or sulfuric acid could exist**, making it a speculative region for possible microbial life.
Is there any place where we might find liquid water on Uranus or Neptune?
Responses

No, these planets are too cold to have liquid water either on their exteriors or inside them.
No, these planets are too cold to have liquid water either on their exteriors or inside them.
Yes, but probably only very deep in their interiors.
Yes, but probably only very deep in their interiors.
Yes, in the clouds of their upper atmospheres.
Yes, in the clouds of their upper atmospheres.
Yes, just under their icy surfaces.
✅ **Correct answer:**
– **Yes, but probably only very deep in their interiors.**

Beneath Uranus’s and Neptune’s cold outer layers, **extreme pressure and temperature** may create **deep layers of superheated water mixed with ammonia and other compounds**, forming a possible internal “ocean.”
The spaceship that orbited Saturn from 2004 to 2017 was named ________.
Responses

MESSENGER
MESSENGER
Osiris-REx
Osiris-REx
New Horizons
New Horizons
Cassini

✅ **Correct answer:**
– **Cassini**
The elements carbon, nitrogen, and oxygen are crucial to life on Earth, at least. Which statement about their abundance in the universe is true?
Responses

They are the 3 most abundant elements besides hydrogen in the universe.
They are the 3 most abundant elements besides hydrogen in the universe.
They are the 3 most abundant elements in the universe.
They are the 3 most abundant elements in the universe.
They are 3 of the 7 most abundant elements in the universe.
They are 3 of the 7 most abundant elements in the universe.
They are among the rarest of chemical elements in the universe.

✅ **Correct answer:**
– **They are 3 of the 7 most abundant elements in the universe.**

💡 **Explanation:** After hydrogen and helium (and a few others like oxygen and neon), **carbon, nitrogen, and oxygen** rank among the **top seven most abundant elements**, making them readily available for forming life-bearing molecules.
On Earth, the fact that water is a polar molecule is critical to life because it allow cell membranes to remain intact.
If we placed cell membranes (from life on Earth) in liquid ammonia, methane, or ethane they would
_____. Another biological property of water that results directly from it being a polar molecule is that
____ .

✅ **Complete answer:**

If we placed cell membranes (from life on Earth) in liquid ammonia, methane, or ethane they would **dissolve or fall apart**, because those liquids are **nonpolar** and cannot support the structure of polar membranes.

Another biological property of water that results directly from it being a polar molecule is that **it is an excellent solvent for ions and polar molecules**, allowing essential **biochemical reactions** to occur inside cells.
Another biological property of water that results directly from it being a polar molecule is that – moles that form H is important, common mole, exists in three phases, or ramin liq <=100c
✅ **Correct answer:**
– **it remains liquid at temperatures less than 100°C**

💧 **Explanation:**
Because water is **polar**, its molecules form **hydrogen bonds** with one another. These bonds give water a **high boiling point**, allowing it to stay liquid over a wide temperature range — a key advantage for sustaining life.
What are Phobos and Deimos?
✅ **Answer:**
**Phobos and Deimos** are the **two small moons of Mars.**

They are **irregularly shaped**, likely **captured asteroids** from the nearby asteroid belt, and orbit Mars very closely — especially **Phobos**, which is slowly spiraling inward and will eventually break apart or crash into the planet.
Which of the following best describes current understanding of Pluto?
Responses

It is an ice-rich world with strong evidence of active geology on its surface.
It is an ice-rich world with strong evidence of active geology on its surface.
It is a rocky, cratered world in the asteroid belt.
It is a rocky, cratered world in the asteroid belt.
It is made of comet-like material and is covered with impact craters.
It is made of comet-like material and is covered with impact craters.
It is almost as large as Earth and has a thick atmosphere.
✅ **Correct answer:**
– **It is an ice-rich world with strong evidence of active geology on its surface.**

🌋 **Explanation:**
Data from *New Horizons* showed Pluto has **glaciers, mountains, and possible cryovolcanoes**, indicating **ongoing geological activity** beneath its icy crust — far more dynamic than previously thought.
Which of the seven other planets (besides Earth) in our solar system have been visited by robotic spacecraft? Select all that apply
Responses

Mercury
Mercury
Mars
Mars
Venus
Venus
Jupiter
Jupiter
Saturn
Saturn
Uranus
Uranus
Neptune
✅ **Correct answers:**
– **Mercury**
– **Venus**
– **Mars**
– **Jupiter**
– **Saturn**
– **Uranus**
– **Neptune**

🛰️ **Explanation:**
Every planet in our solar system has been visited by robotic spacecraft — from *Mariner* and *Venera* missions to *Voyager 2*, which flew past Uranus and Neptune.
Astro 155 done for another 10 days! Now, on to C++?

🎉 Nice work, Rick — you’ve officially cleared another stretch of **Astrobiology 155**. Ten days of freedom from RNA worlds and icy moons.

Yep, time to shift gears — back to **C++ mode**: clean logic, tight syntax, and no speculation about microbes under Europa’s ice. Want to pick up where we left off in Unreal integration or pure C++ fundamentals?