HiRISE Captured Perseverance During Descent to Mars (cropped)

Mars atmospheric entry is the entry into the

atmosphere of Mars The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...

. High velocity entry into Martian air creates a CO₂-N₂ plasma, as opposed to O₂-N₂ for Earth air.J. Louriero, et al. - Atmospheric Entry Research at the Plasma Physics Centre
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 system Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...

s and atmospheric friction have been used historically to reduce most of the

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acce ...

that needs to be lost prior to landing, with

parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...

s and, sometimes, a final bit of

retropropulsion A retrorocket (short for ''retrograde rocket'') is a rocket engine providing thrust opposing the motion of a vehicle, thereby causing it to decelerate. They have mostly been used in spacecraft, with more limited use in short-runway aircraft l ...

used in the final landing. High-altitude high-velocity retropropulsion is being researched for future transport flights landing heavier cargos. For example,

Mars Pathfinder ''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled robot ...

entered in 1997.Mars Pathfinder Atmospheric Entry Strategy - NASA
/ref> 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 Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arr ...

signals for important events.

List of spacecraft

Opportunity heat shield Sol335B P2364 L456-B339R1

Some examples of spacecraft that have attempted to land on the surface of Mars: * 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 ''Viking 1'' was the first of two spacecraft, along with '' Viking 2'', each consisting of an orbiter and a lander, sent to Mars as part of NASA's Viking program. The lander touched down on Mars on July 20, 1976, the first successful Mars la ...

(1975) – successfully landed *

Viking 2 The ''Viking 2'' mission was part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the ''Viking 1'' mission. ''Viking 2'' was operational on Mars for sols ( days; '). The ''Vi ...

(1975) – successfully landed *

(entered atmosphere in 1997) *

Beagle 2 The ''Beagle 2'' is an inoperative British Mars lander that was transported by the European Space Agency's 2003 ''Mars Express'' mission. It was intended to conduct an astrobiology mission that would have looked for evidence of past life on Mar ...

(lost, confirmed landed but derelict in 2015) *

MER-A ''Spirit'', also known as MER-A (Mars Exploration Rover – A) or MER-2, is a Mars robotic rover, active from 2004 to 2010. ''Spirit'' was operational on Mars for sols or 3.3 Martian years ( days; '). It was one of two rovers of NASA's Ma ...

MER-B ''Opportunity'', also known as MER-B (Mars Exploration Rover – B) or MER-1, is a robotic rover that was active on Mars from 2004 until 2018. ''Opportunity'' was operational on Mars for sols (). Launched on July 7, 2003, as part of NASA's ...

Mars Polar Lander The Mars Polar Lander, also known as the Mars Surveyor '98 Lander, was a 290-kilogram robotic spacecraft lander launched by NASA on January 3, 1999, to study the soil and climate of Planum Australe, a region near the south pole on Mars. It form ...

(lost) * Deep Space 2 (lost) *

Phoenix lander ''Phoenix'' was an uncrewed space probe that landed on the surface of Mars on May 25, 2008, and operated until November 2, 2008. ''Phoenix'' was operational on Mars for sols ( days). Its instruments were used to assess the local habitabilit ...

* Mars Science Laboratory (

Curiosity (rover) ''Curiosity'' is a car-sized Mars rover designed to explore the Gale crater on Mars as part of NASA's Mars Science Laboratory (MSL) mission. ''Curiosity'' was launched from Cape Canaveral (CCAFS) on November 26, 2011, at 15:02:00 UTC and l ...

) * Schiaparelli EDM lander (lost) *

InSight Insight is the understanding of a specific cause and effect within a particular context. The term insight can have several related meanings: *a piece of information *the act or result of understanding the inner nature of things or of seeing intui ...

lander (entered atmosphere in 2018) *

Mars 2020 Mars 2020 is a Mars rover mission forming part of NASA's Mars Exploration Program that includes the rover '' Perseverance'', the small robotic, coaxial helicopter '' Ingenuity'', and associated delivery vehicles. Mars 2020 was launched from ...

( Perseverance rover and

Ingenuity helicopter ''Ingenuity,'' nicknamed ''Ginny,'' is a small robotic helicopter operating on Mars as part of NASA's Mars 2020 mission along with the ''Perseverance'' rover, which landed with ''Ingenuity'' attached to its underside on February 18, 2021 ...

) * Tianwen-1 lander and remote camera and Zhurong rover

Technologies

A deployable decelerator like a parachute can slow down a spacecraft after a heat shield.B. P. Smith, et al. - A Historical Review of Inflatable Aerodynamic Decelerator Technology Development
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 Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bot ...

MetNet Mars MetNet is a planned atmospheric science mission to Mars, initiated by the Finnish Meteorological Institute (FMI) and under development by Finland, Russia and Spain. By September 2013, two flight-capable entry, descent and landing systems (ED ...

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 Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

of the descent vehicle during the supersonic retropropulsion phase of the entry and deceleration. More specifically, NASA is carrying out

thermal imaging Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared ...

infrared sensor data-gathering studies of the

SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal o ...

booster controlled-descent tests that are currently, , underway. The research team is particularly interested in the 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 Vertical takeoff, vertical landing (VTVL) is a form of takeoff and landing for rockets. Multiple VTVL craft have flown. The most widely known and commercially successful VTVL rocket is SpaceX's Falcon 9 first stage. VTVL technologies were deve ...

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 by Mars Science Laboratory's Entry, Descent and Landing team at 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). 675608main edl20120809-full

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

Mars Pathfinder EDL

Landing site identification

Concept art for a Mars lander concept as it approaches the surface, illustrating how identifying a safe landing spot is a concern.

References

{{reflist