earth science

Lobate debris apron

Lobate debris apron 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 Lobate debris apron rather than just read about it. In short: Lobate debris aprons (LDAs) are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff.

Key takeaways

Lobate debris apron 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 Lobate debris apron to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lobate debris apron from memory before moving on to harder problems.

Reference excerpt

Lobate debris aprons (LDAs) are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations as do rock glaciers on the Earth.

The Mars Reconnaissance Orbiter's Shallow Radar gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation (between the two reflections). This is evidence that the LDAs in Hellas Planitia are glaciers covered with a thin layer of rocks. In addition, radar studies in Deuteronilus Mensae show that all lobate debris aprons examined in that region contain ice. Analysis of SHARAD data led researchers to conclude that Lobate debris aprons (LDA's) are over 80% pure ice. The paper authors examined five different sites from around the planet and all showed high levels of pure water ice. Because of the high purity of the ice content that was found, the authors argued that the formation of glaciers happened by atmospheric precipitation or direct condensation. After glaciers were formed there was a time when enhanced sublimation formed a lag layer or promoted the accumulation of dry debris atop the water ice glacier. Those dry debris would then insulate the underlying ice from going away. The experiments of the Phoenix lander and the studies of the Mars Odyssey from orbit show that frozen water exists just under the surface of Mars in the far north and south (high latitudes). Most of the ice was deposited as snow when the climate was different. The discovery of water ice in LDAs demonstrates that water is found at even lower latitudes. Future colonists on Mars will be able to tap into these ice deposits, instead of having to travel to much higher latitudes. Another major advantage of LDAs over other sources of Martian water is that they can easily be detected and mapped from orbit. Lobate debris aprons are shown below from the Phlegra Montes which are at a latitude of 38.2 degrees north. The Phoenix lander set down at about 68 degrees north latitude, so the discovery of water ice in LDAs greatly expands the range of water easily available on Mars. It is far easier to land a spaceship near the equator of Mars, so the closer water is available to the equator, the better it will be for colonists.

Lineated floor deposits The floors of some channels show ridges and grooves that seem to flow around obstacles; these features are called lineated floor deposits or lineated valley fill (LVF). Like lobate debris aprons, they are believed to be ice-rich. Some glaciers on the Earth show such features. It has been suggested that lineated floor deposits began as LDAs. By tracing the paths of the curved ridges characteristic of LDAs, researchers have come to believe that they straighten out to form the ridges of LVF. Both lineated floor deposits and lobate debris aprons often display a strange surface formation called brain terrain because it looks like the surface of the human brain.

Reull Vallis, pictured below, displays these deposits. Sometimes the lineated floor deposits show a chevron pattern, which is further evidence of movement. The picture below taken with HiRISE of Reull Vallis shows these patterns.

Recent observations Recent analyses of the Nereidum Montes (~35–45°S, ~300–330°E), and Phlegra Montes (NNE–SSW, between latitudes 30–52°N) mountain ranges of Mars have revealed terrains rich in viscous flow features (VFFs), a cyro-geomorphological group of which lobate debris aprons are a sub-class. In a 2014 study, 11,000 VFFs have been recorded between 40° and 60° in northern and southern latitudes, with a 2020 study identifying approximately 3,348 VFFs in the Nereidum Montes range. These LDAs were more extensive and older VFF features (hundreds of Ma) in the range, with the vast majority located in impact craters and surrounding massifs. Water-ice to lithic ratios of 9:1 were recorded for LDAs by the Mars Reconnaissance Orbiter (MRO), with Berman's 2020 study presenting Nereidum Montes as possibly containing more water-ice rich LDAs, than other locations in the mid-latitude band. Studies have estimated that LDAs could reach from tens of meters up to 390 meters (1,280 feet) in thickness, with anywhere from 1 to 10 meters (3.3 to 32.8 feet) of overlying regolith preventing sublimation. Late Amazonian glaciation may have occurred in the mid-latitudes due to water-ice emplacement from higher latitudes. This glaciation may have occurred during high obliquity periods in Mars past. Some of these LDAs are overlain with another class of viscous ice flows that is smaller, and younger (tens of Ma) called glacial-like flows (GLFs). Some 320 of these superposed GLFs (SGLFs) have been found, implying successive glaciation periods. The datasets utilized in these studies included MRO Context Camera (CTX; ~5–6 m/pixel), High-Resolution Imaging Science Experiment (HiRISE) (~25 cm/pixel) images, MRO Shallow Radar (SHARAD), 128 pixel/degree (~463 m/pixel) Mars Global Surveyor (MGS), Mars Orbiter Laser Altimeter (MOLA), Digital Elevation Modelling (DEM), 100 m/pixel THEMIS Day and Night IR mosaics, and the GIS-based (ESRI ArcGIS Desktop) software. Lobate debris aprons (LDA's) and lineated valley fill (LVF) are now thought to be the same – mostly ice with a covering of debris, their shapes are dependent on their locations. When confined within a valley, LVF is present; in contrast when not confined, this flowing debris covered ice forms LDA's.

More images of glaciers

Illustrations

Worked examples

Example 1 — a first encounter with Lobate debris apron

Start with the simplest possible case. Write down what Lobate debris apron 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 Lobate debris apron 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 Lobate debris apron 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 Lobate debris apron

In research: Lobate debris apron 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 Lobate debris apron 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: Lobate debris apron is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of Mars, Surface features of Mars, so understanding it makes those chapters shorter.
In everyday life: Look for Lobate debris apron 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 Lobate debris apron in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lobate debris apron 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 Lobate debris apron out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lobate debris apron in simple terms?

Why does Lobate debris apron 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 Lobate debris apron?

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 Lobate debris apron.