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by Tilman Spohn, Chief Scientist for the Heat Flow and Physical Properties Package (HP3) experiment aboard NASA’s InSight mission

After some warm “happy summer” wishes, Tilman Spohn summarizes the successful removal of HP3’s Support and Assembly Structure (SSA) early last July in order to expose the MOLE penetrator and facilitate the restoration of its journey to the subsurface.
It was thus seen that MOLE was stuck with still 5 cm of the penetrator itself out of the ground, confirming the team’s suspicions about MOLE getting stuck soon after exiting the SSA guides.
In particular, the width of the hole created by MOLE (about 6 cm wide, or twice the diameter of the probe itself) and the consequent absence of friction with the Martian sand, seem to confirm this theory. In fact, the images show us how MOLE has rotated 135° on itself in a clockwise direction, causing also a multiple rebound of SSA evidenced by the footprints left on the Martian soil by the feet of the structure itself during the operations of pounding of the soil. Also from the images, it was seen that the cavity created by MOLE was about 7-8 cm deep. It was understood that a layer about 5-10 cm thick of solid soil or cemented sand had been found.
In July, it was believed that this layer of “solid crust” was easily crushed and it was decided to continue by pressing the surrounding soil to cause a collapse of the material around MOLE in order to increase its friction with the soil itself. Three attempts were made during the month of August, unfortunately without being able to cause a total collapse but only partial. From these attempts it was concluded that under a layer about 1 cm thick of sand there was a layer of “hard crust” resistant to a pressure of several hundred Chilopascals equivalent to several kilograms per square centimeter.
The statement concludes by saying that, due to the Mars-Sun conjunction and the consequent absence of communication with Mars, the InSight team will go on vacation until September 10. In the meantime Tilman Spohn will think about other strategies to solve the problem, including the possibility of acting directly with the robotic arm on MOLE, even if the operation could put at risk the integrity of the penetrator itself.
After September 10, Tilman Spohn will let us know the final decision that will be made by his team.

Free translation of the post:
“Logbook entry August 27, 2019”

Personal Considerations:
I find the design error of HP3 and MOLE truly absurd, based on the absurd assumption that the penetrator would only encounter soft sand or at most a few small, easily scalable pebbles.
Elysium Planitia, the landing site of InSight, is known as a volcanic area where, in spite of its smooth and regular appearance, there may be layers of hard rock just below the sandy surface.
As if that wasn’t enough, Elysium Planitia is rich in frozen water as we read from Wikipedia:
“A photo of Elysium Planitia taken by the Mars Express spacecraft in 2005 shows that it may be covered with water ice. It has been estimated that the volume of ice may be 800 to 900 km across and 45 m deep, very similar in width and depth to the North Sea.
The ice is thought to be the result of the remnants of some water flooding and lava flows in the Cerberus Fossae (Cerberus Pits), surface cracks dated to approximately 2 to 10 million years ago.”
So MOLE may very well have encountered a massive ice layer as well!
In any case, ice layer or rock layer, I have very strong doubts that MOLE can resume drilling the Martian soil and reach the five meters of depth expected, simply it has been poorly designed or it has chosen the wrong site only for the ease of landing.
When will they realize this?

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