Chapter 4 Icy Bodies Flashcards
What causes the ball of string appearance on Europas surface?
These small ridges are believed to be caused by surface extension due to tidal stressing. When the cracks close, they push slush to the surface to form the ridge.
Why is the older ice lighter than the new ice?
The newer ice is highly concentrated with salts. Over time the salts break down due to photolysis and radiolysis, leaving a purer ice.
What are chaos areas on Europa?
These are areas that have been subjected to sub-surface hot spots causing the surface to melt. ‘Rafts’ of the ball of string surface break off and float into the newly formed surface.
Conventionally, within a chaos region, the detached slabs of ball-of-string surface are referred to as rafts and the low-lying hummocky material in between is called matrix.
What is the matrix of a chaos zone?
It is most commonly the re-frozen surface of an ocean that was exposed when overlying ice was removed, presumably by melting caused by an episode of heating below.
Why are craters less evident on the matrix compared to on the rafts?
The craters on the rafts were preserved from before the formation of chaos.
The matrix surface is very rough and therefore hard to see craters.
The matrix may have been mobile for some time after chaos formation, destroying evidence of impacts.
What evidence is there that chaos with form “ball of string” terrain?
New forming ridges appear to cut across both rafts and matrix.
After enough new ridges form the chaos may lose its integrity and take on the “ball of string” appearance.
How can chaos be used to estimate ice thickness? (equation)
Assuming that matrix was the water level, we can use the height of the rafts above the matrix ( by measuring the cliff shadow) to calculate the depth of the raft below the surface.
Assuming the densities of the ice based or salt and fresh water the formula
ρ1(h+w) = ρ2w
Where ρ1 and ρ2 are raft and liquid density respectively and h is height of raft about water and w is depth of raft below the surface.
Can be used to estimate ice thickness at the time chaos was produced.
Calculation for pressure at depth beneath ice.
P = ρgd
Where ρ is the density of the ice, g is acceleration due to gravity and d is depth.
Why is Europas surface uninhabitable?
Cold temperatures of -140°
Within Jupiters magnetosphere means it’s bombarded with charged particles.
Why is it uncertain if hydrathemal vents are present on Europa?
We are unsure if tidal heating mainly takes effect in the icy steel of Europa or in its core.
If the underlying ocean is heated from above we con assume it to be nutrient poor, if its heated from below we can assume it to be nutrient rich due to hydrothermal activity.
What evidence points to Europas ocean being reduced?
The immense pressure at the bottom Europas ocean would favour methane production.
What evidence points to Europas ocean being oxidised?
Photolysis and radiolysis causes water molecules to break down to oxygen and hydrogen. Hydrogen is lost to space easily but oxygen may become trapped in ice and eventually incorporated into the ocean.
Potassium - 40 can be responsible for radiolysis below the ice.
Is Enceladus a viable place to find life?
Enceladus is suspected to have a 10 km global ocean covered by 30 to 40 km of ice. Orbiters have shown that icy plume is erupting from Enceladus are mainly water and contain a variety of organic molecules using mass spectrometry.
It is suspected that the ocean is operating above 90°C due to molecules containing silica being found. They form from olivine at high temperatures.
Do Ganymede and Callisto contain oceans?
Although these moons are for feather from Jupiter orbiters show that they both contain magnetic fields suggesting that each does have on internal ocean.
Jupiters magnetic field is also distorted in the region of Callisto, yet more evidence of a ten km top ocean at a depth of a few hundred km creating an induced magnetic field.
Ganymede generates its own magnetic field as well as having an induced magnetic field which suggests that it has a liquid iron core as well as an ocean similar to Callisto.
