InSight Surface Operations, 26 Nov 2018- 21 Dec 2022 Options

[Phil Stooke]

Return to a weekly cadence to speed things up? On sol 700 soil was scraped over the hole again. On sol 707 the arm was placed over the mole just above the surface, probably to press down and compact the soil again.

Phil

[Phil Stooke]

No, no change in the 2 week operations. On sol 720 the scoop has just been pushed down to compress the sol 700 soil pile.

Phil

[PaulH51]

No, no change in the 2 week operations. On sol 720 the scoop has just been pushed down to compress the sol 700 soil pile.

processed GIF using the 3 available IDC images

[PaulH51]

'End Game for HP3'

In the last paragraph of this Nature.com article dated December 15..

Along with listening to marsquakes, InSight’s other big scientific goal is to measure heat flow through the Martian ground using a probe dubbed the mole. It was meant to bury itself deep in the soil, but has struggled to do so — at one point even popping out of the ground altogether. The mole has finally managed to get itself several centimetres deep, says Banerdt, and will try digging one final time in the coming weeks before giving up. “We’re at what we consider to be the end game now,” he says.

[MahFL]

'End Game for HP3'

Bummer.

[Phil Stooke]

Yes, indeed.

Phil

[stevesliva]

Well, the "no digging till 2021" is now combined with "if that doesn't work-- that's it."

Here's hoping it works.

[JRehling]

As a baseball fan, I'm familiar with the state of affairs where you're behind but suddenly win on the last play of the game. I'll hold out hope until that final attempt concludes.

If it does fail, I hope that a heat probe can be flown on a subsequent mission in the foreseeable future.

[Gerald]

The rheology of the Martian soil appears to differ significantly from expectations.
Wouldn't it be worth to redefine the science objective of the mole (and of the scoop) to learn more about the mechanical properties of Martian soil?
Those data might turn out relevant for future heat probes as well as for rover design and operation.
Who knows, maybe the results could even be used to resume the primary science goal, provided, of course, the lander will stay operational for long enough.

[JRehling]

Some of the speculation from the team included the possibility that the soil at the landing site may have differed, crucially, from that at other locations. Obviously, there's no way to know this with any detail or certainty, but it could be that simply landing somewhere else might have led to success of the mole. Certainly, the properties of Earth's soil different enormously from one location to another, and there's no doubt that this is also true on Mars, but we can't know conclusively that the same failure wouldn't have happened at any other location.

As I mentioned far upthread, the first effort to place a probe in the lunar surface was unexpectedly difficult, and even after a redesign, the second effort was also unexpectedly difficult, and this was true even when there were astronauts in the loop to modify the approach on the spot.

Also, to be precise, the Deep Space 2 probes were in a sense one or two earlier attempts to get a probe into the martian subsurface, but we didn't learn the cause of failure in that case.

The mole was a rather idiosyncratic architecture – perhaps a wise one given the knowledge we had at the time – but there are other, radically different options. Perhaps the best path forward is not to refine the Insight mole so much as to try a different tack, just as the unfortunate happenstance of the Galileo probe entry site was solved not with another entry probe but a completely different approach (Juno).

[Gerald]

Shouldn't we try to squeeze out as much science as reasonably possible with the assets that are already available on Mars, even if this might require to redefine the science objectives?
One reliable data point would be better than speculation.
Soil properties may vary elsewhere, but deposits of settled dust should be quite ubiquitious on Mars.
Think at future applications, for example, at kind of a hammering mechanism for a rover to self-liberate when getting stuck in such a dust deposit, or at a method to cross dunes with kind of a hopping mechanism rather than roving. Any such considerations would require data. Now is the opportunity to collect some of them.

But first let them perform their planned attempt to address the initial science objective...

[mcaplinger]

Shouldn't we try to squeeze out as much science as reasonably possible with the assets that are already available on Mars...

What are you suggesting they do that they haven't done already?

[Gerald]

In case the next hammering attempt won't work in the intended way, and the mole would otherwise be given up, I'd suggest to further narrow down the root cause of the presumed bouncing.

One activity would be an attempt to verify with the scoop that there actually isn't a pebble, bedrock, or another crust layer, i.e. perform some digging. The goal is to ensure that the behaviour of the mole is unambigously caused by the property of the fine-grained soil phases. A first digging campaign would be performed in a safe distance from the mole to study the general layering structure of the soil. If this doesn't find obvious obstacles, digging next to the mole may be considered. This latter location would also be the only option to dig, if the upper duricrust turns out that it can't be penetrated by the scoop alone.

Another conceivable explanation to be ruled out is whether the density of the mole is less than the density of the soil, which would cause bouyancy.

Other experiments would repeat (cautious) hammering with different inclinations of the mole in order to get responses within a more homogenious soil environment. The bouncing might be caused by the vertical gradient of some property of the soil. If such a gradient exists, it would be smaller for a less inclined mole, with a possibly favorable change of its behaviour, but at least with additional data about inclination-dependent soil behaviour. A less inclined mole would also be able to discriminate between bouyancy (parallel to the gravity field lines) and bouncing (parallel to the hammering vector).

Since I'm not an expert in rheology, but this is a broad field of ongoing research, a student or post-doc in rheology would certainly give more advice than I could.
As usual, any experiments should be sorted by increasing risk. And I'm of course aware that things are much easier said than done.

[Brian Swift]

And I'm of course aware that things are much easier said than done.

I'll speculate the termination of further investigation is primarily a matter personnel scheduling and budget.
Implementing these ideas would require a non-trivial amount of engineering time. And if "the system" is working
well, those engineers are already scheduled to be working on and receiving their funding from other projects in 2021.
I imagine that some amount of the project's reserves budget has already been consumed by mole engineering work done in 2020.
And reducing a projects reserves budget is another form of risk.

[stevesliva]

Yeah, soil investigations would be an XM sort of thing. But it might not pencil out.

Primary mission was to be 709 sols and we're past 730? Wonder what's up there.

Different topic.
In addition to the Nature article with the "final try" comment, I notice there's a JPL release from a couple days ago, which doesn't say much about the mole:
https://www.jpl.nasa.gov/news/news.php?feature=7802