Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. It's assumed that, even if Europa has life, the total amount of that life will be small. That's because (a) Europa is only about as big as our own Moon, and consequently there's not much room for life; (b) the ocean will be cold, slowing down metabolism; (c) there are likely to be only limited sources of energy for life.

Short answer

The best answer is (c); energy sources are crucial for sustaining life.

Step-by-step solution

Understanding Europa's Size

Europa is compared to Earth's Moon in size. Since Europa is relatively small, the total surface area and volume available for organisms to reside is limited, suggesting that if life exists, its potential abundance may be restricted. This makes option (a) a plausible reason for limited life.

Examining Ocean Temperature

Europa's ocean is expected to be cold. Lower temperatures can reduce metabolic rates in organisms, meaning that life processes could occur more slowly and might limit the amount of biomass present. This supports option (b) as a reason for the expected small amount of life.

Evaluating Energy Sources

Limited energy sources on Europa could mean fewer nutrients and less energy for life forms to sustain themselves or grow. Energy is crucial for metabolic activities, and a deficiency could restrict biological abundance. This makes option (c) a strong reason for the assumption of limited life.

Choosing the Best Answer

While all options suggest plausible reasons for limited life on Europa, option (c) is likely the best answer because energy is a fundamental requirement for life. Without adequate energy sources, life would struggle to develop, regardless of space available or temperature conditions.

Key concepts

Europa

Europa is one of Jupiter's intriguing moons. Its size is comparable to that of our Moon, making it relatively small in the vast cosmos.
The surface of Europa is primarily ice, but beneath this icy exterior, scientists propose the existence of a vast, subsurface ocean.
This ocean is nearly twice the volume of all Earth's oceans combined, making it a prime candidate for exploring the potential of life beyond our planet.
Although Europa's surface is cold, the ocean underneath might be kept warm by tides created from Jupiter’s gravitational pull.

• This tidal heating is thought to keep the water in a liquid state.
• The ice layer helps protect the ocean from the intense radiation coming from Jupiter.

Exploring Europa can be challenging due to its distance from us and the icy crust that conceals its oceans. Scientists believe that studying Europa can help us understand the potential for life in environments vastly different from Earth.

extraterrestrial life

The quest for extraterrestrial life is one of the greatest scientific pursuits of our time.
Europa is a focal point in this search due to its subsurface ocean, which could harbor life.
Life beyond Earth might differ significantly from what we know, existing in places previously thought uninhabitable.
When talking about extraterrestrial life, scientists often rely on life as we know it — carbon-based organisms that require liquid water and an energy source.

• Many scientists believe that Europa's ocean could provide these conditions.
• Life forms in such an environment might resemble microorganisms found in Earth's deep-sea vents.

The discovery of life elsewhere would profoundly impact our understanding of biology, the origin of life, and our place in the universe. It would suggest that life might not be unique to Earth, but common where conditions permit.

habitable environments

A habitable environment supports life as we understand it.
Europa presents aspects of what could be such an environment with its significant subsurface ocean kept warm by tidal heating.
On Earth, similar environments inspire scientific fascination, such as hydrothermal vents on the ocean floor.

• These vents support complex ecosystems, thriving without sunlight and relying on chemicals as energy sources.
• Europa's ocean floor might have hydrothermal vents, creating an environment where life could potentially exist.

However, habitability requires more than just water. The conditions must include nutrient availability and stable energy sources.
Europa's icy shell may act as a barrier against radiation, creating a possibly stable environment beneath for microbial life to flourish.

energy sources for life

Energy is essential for all life forms, supporting processes like metabolism and reproduction.
On Earth, sunlight is a primary energy source, but not all environments receive sunlight.
In places like the deep ocean, life relies on energy from chemical reactions.
On Europa, potential energy sources could include:

• Tidal heating from gravitational interactions with Jupiter, which keeps the ocean liquid.
• Possible hydrothermal activity on its ocean floor, similar to Earth's hydrothermal vents where chemicals like hydrogen sulfide provide energy.

Without viable energy sources, sustaining life becomes exceedingly difficult, regardless of the presence of water or nutrient-rich conditions.
This makes understanding energy sources crucial when assessing the potential for life on celestial bodies like Europa.