InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport)

1. Historical Context and Detailed Objectives

The scientific gap that the InSight mission aimed to fill lay in the absence of deep geophysical data on rocky planets other than Earth. Primary objectives focused on understanding the evolutionary processes in the formation of terrestrial worlds by studying the interior of Mars.

Engineering:

• Validate the fixed surface lander platform for prolonged geophysical operations.
• Operate the robotic arm (Instrument Deployment Arm) for the precise placement of instruments on the Martian terrain.

Scientific:

• Determine the size, state, and composition of the Martian core.
• Establish the structure and thickness of the crust and mantle.
• Measure internal heat flow using a penetrating sensor.
• Record seismic activity (marsquakes) and planetary rotation.

2. Vehicle Architecture and Main Subsystems

The total launch mass of the spacecraft was 694 kg, distributed as 358 kg for the lander, 189 kg for the aeroshell, 79 kg for the cruise stage, and 67 kg for propulsion and pressurants. The module featured a wingspan of 6.0 m with solar panels deployed, a deck diameter of 1.56 m, and a deck height of between 83 and 108 cm. Its power system consisted of two circular solar panels capable of generating between 600 and 700 W under optimal daytime conditions. Communications were managed via X-band and UHF antennas, supported by the Deep Space Network and relay orbiters.

3. Payload and Scientific Instrumentation

• SEIS (Seismic Experiment for Interior Structure): Ultra-high precision seismometer provided by CNES to record seismic waves and internal vibrations.
• HP³ (Heat Flow and Physical Properties Package): Radiometer and heat flow probe ("the mole") developed by DLR to measure internal thermal flux.
• RISE (Rotation and Interior Structure Experiment): Radio science experiment to study the wobble and rotation of the planetary core.
• APSS (Auxiliary Payload Sensor Suite): Set of meteorological and magnetic sensors to calibrate seismic signals by eliminating environmental noise.
• IDA (Instrument Deployment System): Robotic arm equipped with a camera to position the equipment.
• LaR (Laser Retroreflector): Laser retroreflector for precision geodetic localization.

4. Chronology and Mission Phases

The mission lifted off on May 5, 2018, from Vandenberg and completed its insertion and descent on November 26, 2018, in Elysium Planitia. After the first sols of characterization, the official scientific phase began in early 2019 with instrument deployment. During the 2019-2021 period, numerous quakes were recorded and technical difficulties with the HP³ probe were tackled. On April 24, 2022, the last selfie was completed before energy degradation, with definitive contact lost on December 15, 2022. NASA formally declared the end of the mission on December 21, 2022.

5. Results and Discoveries

InSight detected more than 1,300 marsquakes, allowing for the first-ever mapping of the internal structure of a rocky planet other than Earth. It was determined that the Martian crust has a thickness of between 20 and 70 km, the size of the mantle was delimited, and it was confirmed that the liquid core is unusually large and rich in light elements. Additionally, APSS data expanded knowledge on local atmospheric dynamics and crustal magnetic remanence.

6. Legacy and Significance

The mission formally concluded due to the irreversible depletion of energy in its batteries caused by the massive accumulation of Martian dust on the solar panels. Its legacy endures as the first milestone in in-situ planetary seismology on Mars, laying the methodological foundations for comparative geophysics in the solar system.