Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of the following is not an indication of liquid water beneath Europa's icy surface? (a) the moon's changing magnetic field; (b) the moon's average density; (c) surface features that look like jumbled icebergs.

Short answer

(b) the moon's average density does not indicate liquid water.

Step-by-step solution

Understand the properties of Europa

Europa is one of Jupiter's moons, known for a thick ice shell covering a subsurface, which scientists suggest could be a vast ocean of liquid water beneath. Important indicators include observing changes due to Europa's magnetic field and surface characteristics.

Analyze the significance of the magnetic field

Europa's changing magnetic field suggests the presence of a saline ocean beneath the ice, which conducts electricity and influences the magnetic field, providing indirect evidence of liquid water.

Evaluate the relevance of moon's average density

Europa's average density indicates its composition is largely rock and metal, but does not directly reveal the existence of liquid water. This measurement alone isn't an indicator of liquid properties beneath the surface.

Interpret the surface features

Surface features resembling jumbled icebergs may imply ice movement over a liquid water base, suggesting the underlying ocean allows for such movement, thus indicating the presence of liquid.

Choose the answer

Given the information, (a) and (c) both suggest evidence of liquid water beneath the surface. However, (b) the moon's average density does not directly point to the presence of liquid water.

Key concepts

Magnetic Field

Europa's magnetic field is a fascinating aspect of its character. Among the many details that researchers pore over, its changing magnetic field stands out. But why does this matter? Well, a continuously varying magnetic field around Europa suggests active processes beneath its icy shell.

Scientists believe that beneath this shell lies a salty, liquid ocean. How does this relate to the magnetic field? When a moon or planet's magnetic field changes, it's often due to something conductive beneath the surface. In Europa’s case, the ocean could consist of salty water, which conducts electricity just like the oceans on Earth.

Here’s what happens:

• The ocean's salt content could allow it to support electric currents.
• These currents can influence Europa's magnetic field, causing observable variations.

Therefore, by studying these magnetic fluctuations, scientists gain indirect but compelling evidence of a liquid water ocean beneath Europa's ice-covered surface.

Average Density

The average density of Europa provides critical insights into the moon's overall composition. To fully grasp its role, we need to understand what density represents. Density is the mass of an object divided by its volume, and it helps establish what materials comprise a celestial body.

Europa's density is measured to be around 3 grams per cubic centimeter, suggesting a composition mostly of rock and metal, similar to terrestrial planets.

It's important to note:

• A high average density signifies heavier elements like rock and metal are present.
• This metric doesn't directly indicate the presence of water, especially liquid water.

Thus, while Europa's average density tells us a lot about its internal makeup, it’s not a direct indicator of an ocean beneath its icy crust. The density gives us a broad picture without diving into specific components like subsurface liquids.

Surface Features

Europa's surface features provide exciting clues about the moon's hidden secrets. These surface characteristics have intrigued scientists for years due to their peculiar nature. Among them, features resembling jumbled icebergs are particularly compelling.

These features imply more than just a frozen landscape:

• The 'jumbled iceberg' appearance suggests ice plates or chunks have moved, possibly floating on or interacting with a liquid ocean below.
• Such formations would be challenging to form without a soft, possibly liquid-like base allowing movement and re-arrangement of ice sheets.

These observations align with the hypothesis of liquid water underneath Europa's surface. The movement and reorganization of surface ice over time offer strong evidence of an underlying, possibly vast ocean acting as a dynamic force.