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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.^[1] Mars entry is effected by the radiative effects of hot CO₂ gas and Martian dust suspended in the air.^[2] Flight regimes for entry, descent, and landing systems include aerocapture, hypersonic, supersonic, and subsonic.^[3]

For example Mars Pathfinder entered in 1997.^[4] About 30 minutes prior to entry, the cruise stage and entry capsule separated.^[4] When the capsule hit the atmosphere it de-accelerated from about 7.3 km/s to 0.4 km/s (16330 mph to 900 mph) over three minutes.^[4] As it descended the parachute opened to slow it down further, and soon after the heat shield was released.^[4] During entry a signal was relayed back to Earth, including semaphore signals for important events.^[4]

Comparison of altitude (y-axis) and velocity (x-axis) of various Mars landers

Parachute of Phoenix lander open as it descends in the Martian atmosphere. This picture was taken by the Mars Reconnaissance Orbiter with HiRISE

MSL heat shield

Examples [edit]

MER-B's discarded heat shield on the surface of Mars.

• Mars 2
• Mars 3
• Mars 6
• Viking 1
• Viking 2
• Mars Pathfinder
• MER-A
• MER-B
• Phoenix lander
• Mars Science Laboratory

Technologies [edit]

A deployable decelerator like a parachute can slow down a spacecraft after a heat shield.^[5] Typically a Disk-Gap-Band parachute has been used, but another possibility are trailing or attached inflatable entry devices.^[5] 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.^[5] Viking-era researchers were the true pioneers of this technology, and development had to be restarted after decades of neglect.^[5] Those latest studies have show that tension cone, isotensoid, and stacked torus may be the best types to pursue.^[5]

Finland's MetNet probe may use an expandable entry shield if it is sent.^[6] Martian air can also be used for aerobraking to orbital velocity (aerocapture), rather than descent and landing.^[1] Supersonic retro-propulsion is another concept to shed velocity.^[7]

Example [edit]

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).^[8]

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

References [edit]

Further reading [edit]

• Atmospheric entry profiles from the Mars Exploration Rovers (.pdf)
• Overview of Dust Effects During Mars Atmospheric entries (.pdf)

See also [edit]

• Mars landing
• Venus atmospheric entry