earth science

Mars atmospheric entry

Mars atmospheric entry 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 Mars atmospheric entry rather than just read about it. In short: Mars atmospheric entry is the entry into the atmosphere of Mars. High velocity entry into Martian air creates a CO2-N2 plasma, as opposed to O2-N2 for Earth air.

Key takeaways

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

Reference excerpt

Mars atmospheric entry is the entry into the atmosphere of Mars. High velocity entry into Martian air creates a CO2-N2 plasma, as opposed to O2-N2 for Earth air. Mars entry is affected by the radiative effects of hot CO2 gas and Martian dust suspended in the air. Flight regimes for entry, descent, and landing systems include aerocapture, hypersonic, supersonic, and subsonic.

Overview Thermal protection systems and atmospheric friction have been used historically to reduce most of the kinetic energy that needs to be lost prior to landing, with parachutes and, sometimes, a final bit of retropropulsion used in the final landing. High-altitude high-velocity retropropulsion is being researched for future transport flights landing heavier cargos. For example, Mars Pathfinder entered in 1997. About 30 minutes prior to entry, the cruise stage and entry capsule separated. When the capsule hit the atmosphere it decelerated from about 7.3 km/s to 0.4 km/s (16,330 mph to 900 mph) over three minutes. As it descended the parachute opened to slow it down further, and soon after the heat shield was released. During entry a signal was relayed back to Earth, including semaphore signals for important events.

List of spacecraft Mars 2 (1971) – entered atmosphere but crashed Mars 3 (1971) – entered atmosphere, soft landed, lost after 20 seconds of data transmission from the surface Mars 6 (1973) – entered atmosphere but crashed Viking 1 (1976) – successfully landed Viking 2 (1976) – successfully landed Mars Pathfinder (1997) – successfully landed Beagle 2 – lost, confirmed landed but derelict in 2015 MER-A "Spirit" – successfully landed MER-B "Opportunity" – successfully landed Mars Polar Lander (lost) Deep Space 2 (lost) Phoenix lander – successfully landed Mars Science Laboratory (Curiosity rover) – successfully landed Schiaparelli EDM lander (lost) InSight lander (2018) – successfully landed Mars 2020 (Perseverance rover and Ingenuity helicopter) – successfully landed Tianwen-1 lander and remote camera and Zhurong rover – successfully landed

Technologies

A deployable decelerator like a parachute can slow down a spacecraft after a heat shield. Typically a Disk-Gap-Band parachute has been used, but another possibility are trailing or attached inflatable entry devices. Inflatable types include sphere w/ fence, teardrop w/ fence, isotensoid, torus, or tension cone and attached types include isotensoid, tension cone, and stacked toroid blunted cone. Viking Program era researchers were the true pioneers of this technology, and development had to be restarted after decades of neglect. Those latest studies have shown that tension cone, isotensoid, and stacked torus may be the best types to pursue. Finland's MetNet probe may use an expandable entry shield if it is sent. Martian air can also be used for aerobraking to orbital velocity (aerocapture), rather than descent and landing. Supersonic retro-propulsion is another concept to shed velocity. NASA is carrying out research on retropropulsive deceleration technologies to develop new approaches to Mars atmospheric entry. A key problem with propulsive techniques is handling the fluid flow problems and attitude control of the descent vehicle during the supersonic retropropulsion phase of the entry and deceleration. More specifically, NASA is carrying out thermal imaging infrared sensor data-gathering studies of the SpaceX booster controlled-descent tests that are currently, as of 2014, underway. The research team is particularly interested in the 70–40-kilometer (43–25 mi) altitude range of the SpaceX "reentry burn" on the Falcon 9 Earth-entry tests as this is the "powered flight through the Mars-relevant retropulsion regime" that models Mars entry and descent conditions, although SpaceX is of course interested also in the final engine burn and lower velocity retropropulsive landing as well since that is a critical technology for their reusable booster development program which they hope to use for Mars landings in the 2020s.

Examples

Mars Science Laboratory The following data were compiled for the Mars Science Laboratory (Curiosity rover) by the Entry, Descent and Landing team at the NASA's Jet Propulsion Laboratory. It provides a timeline of critical mission events that occurred on the evening of August 5 PDT (early on August 6 EDT).

Curiosity's EDL team releases a timeline for mission milestones (depicted in this artist's concept) surrounding the landing of the Mars rover.

Landing site identification Concept art of a Mars lander as it approaches the surface, illustrating how identifying a safe landing spot is a concern.

See also Mars landing Venus atmospheric entry Hypercone (spacecraft)

References

Further reading Atmospheric entry profiles from the Mars Exploration Rovers (.pdf) Overview of Dust Effects During Mars Atmospheric entries (.pdf) Ensuring safe landings on Mars - Nature 2009

Illustrations

Worked examples

Example 1 — a first encounter with Mars atmospheric entry

Start with the simplest possible case. Write down what Mars atmospheric entry 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 Mars atmospheric entry 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 Mars atmospheric entry 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 Mars atmospheric entry

In research: Mars atmospheric entry 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 Mars atmospheric entry 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: Mars atmospheric entry is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atmosphere of Mars, Exploration of Mars, Extraterrestrial atmosphere entry, so understanding it makes those chapters shorter.
In everyday life: Look for Mars atmospheric entry 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 Mars atmospheric entry in 20 minutes

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

Frequently asked questions

What is Mars atmospheric entry in simple terms?

Mars atmospheric entry is the entry into the atmosphere of Mars. High velocity entry into Martian air creates a CO2-N2 plasma, as opposed to O2-N2 for Earth air.

Why does Mars atmospheric entry 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 Mars atmospheric entry?

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 Mars atmospheric entry.