Initial Results From the Heat Flow and Physical Properties Package (Hp3) on InSight

Date: 4/25/2019

Time: 08:45 AM

Room: Vashon

On Nov 26th, 2018, the NASA InSight mission landed on Elysium Planitia, Mars, as the first geophysical observatory on another terrestrial planet. The payload includes the Heat Flow and Physical Properties Package (HP3) to measure geothermal heat flux at the landing site. By constraining planetary heat flow, HP3 data will inform models of crustal thickness, radioisotope inventory, and planetary evolution.

HP3 consists of a mechanical hammering device called the "Mole” for penetrating into the regolith, an instrumented tether for measuring the subsurface thermal gradient, and an infrared radiometer (RAD) for measuring surface brightness temperature. Reconstruction of the mole's subsurface path, to determine final depths of the temperature sensors, is accomplished with measurements of the mole orientation vector and the extracted tether length. The Mole also includes active heaters and temperature sensors to measure the regolith thermal conductivity to better than 3.5%.

Heat flow is calculated by multiplying the geothermal gradient and the regolith thermal conductivity. Modeling suggests that at Elysium Planitia the surface heat flow is close to the Mars' average value.

The properties of the landing site are favorable for HP3 with an absence of significant slopes and surface rocks. The Mole is planned to penetrate to a depth of 3 - 5 meters. Achieving the required 3 meter depth reduces contributions of surface temperature variations to within mission requirements. Greater depths further reduce these noise sources and thus total measurement time.

Assuming deployment by the end of January and Mole penetration taking the planned 44 sols, the instrument should be fully emplaced by the time of the SSA conference. The RAD is acquiring hourly measurements nearly continuously since sol 24 and determinations of surface thermal inertia are forthcoming. We expect to have measured the regolith thermal conductivity at 50 cm intervals down to the mole's final depth and will have the first data on the temperature gradient below the annual thermal skin depth.

Presenting Author: William B. Banerdt

Authors