earth science

Latitude dependent mantle

Latitude dependent mantle is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Latitude dependent mantle rather than just read about it. In short: Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past. In some places a number of layers are visible in the mantle.

Key takeaways

Latitude dependent mantle belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Latitude dependent mantle to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Latitude dependent mantle from memory before moving on to harder problems.

Reference excerpt

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past. In some places a number of layers are visible in the mantle. It fell as snow and ice-coated dust. There is good evidence that this mantle is ice-rich. The shapes of the polygons common on many surfaces suggest ice-rich soil. High levels of hydrogen (probably from water) have been found with Mars Odyssey. Thermal measurements from orbit suggest ice. The Phoenix (spacecraft) discovered water ice with made direct observations since it landed in a field of polygons. In fact, its landing rockets exposed pure ice. Theory had predicted that ice would be found under a few cm of soil. This mantle layer is called "latitude dependent mantle" because its occurrence is related to the latitude. It is this mantle that cracks and then forms polygonal ground. This cracking of ice-rich ground is predicted based on physical processes. Another type of surface is called "brain terrain" as it looks like the surface of a human brain. Brain terrain lies under polygonal ground when the two are both visible in a region.

Since the top, polygon layer is fairly smooth although the underlying brain terrain is irregular; it is believed that the mantle layer that contains the polygons needs to be 10–20 meters thick to smooth out the irregularities. The mantle layer lasts for a very long time before all the ice is gone because a protective lag deposit forms on the top. The mantle contains ice and dust. After a certain amount of ice disappears from sublimation the dust stays on the top, forming the lag deposit. The total amount of water locked up in the mantle has been calculated based on the total area of polygonal ground and an estimated depth of 10 meters. This volume is equal to a layer 2.5 meters deep spread over the entire planet. This compares to a 30-meter depth over the whole planet for the water locked up in the north and south polar caps. Mantle forms when the Martian climate is different than the present climate. The tilt or obliquity of the axis of the planet changes a great deal. The Earth’s tilt changes little because our rather large moon stabilizes the Earth. Mars only has two very small moons that do not possess enough gravity to stabilize its tilt. When the tilt of Mars exceeds around 40 degrees (from today's 25 degrees), ice is deposited in certain latitude bands where much mantle exists today.

Worked examples

Example 1 — a first encounter with Latitude dependent mantle

Start with the simplest possible case. Write down what Latitude dependent mantle claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Latitude dependent mantle before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Latitude dependent mantle ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Latitude dependent mantle

In research: Latitude dependent mantle appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Latitude dependent mantle in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Latitude dependent mantle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of Mars, so understanding it makes those chapters shorter.
In everyday life: Look for Latitude dependent mantle outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Latitude dependent mantle in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Latitude dependent mantle means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Latitude dependent mantle out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Latitude dependent mantle in simple terms?

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past. In some places a number of layers are visible in the mantle.

Why does Latitude dependent mantle matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Latitude dependent mantle?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Latitude dependent mantle.