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In an interview in the recent article Mars Has So Much Radiation, Any Signs of Life Would Be Buried Six Feet Under physicist Alexander Pavlov of NASA's Goddard Space Flight Center tells that he and his research team found out that amino acids are destroyed by cosmic rays at much faster rates than previously thought.
At the max. 6 cm depth that Perseverance drills down it would take only 20 million years to destroy amino acids completely.
From the abstract of the research article Rapid Radiolytic Degradation of Amino Acids in the Martian Shallow Subsurface: Implications for the Search for Extinct Life:

Our experimental results suggest serious challenges for the search of ancient amino acids and other potential organic biosignatures in the top 2 m of the martian surface.

Emphasis by me.

Now, drilling down to 2 m. is just what the ExoMars drill unit is capable of !
This video shows how the already been built and tested ExoMars drill unit works.

So now it appears that the samples taken by Perseverance will have only a very small chance to contain biosignatures, isn't it justified, regarding future and already spend costs and time, to send an extra rover equipped with the ExoMars drill unit that has a far better chance in getting samples containing biosignatures, prior to the Mars sample return mission ?

This rover wouldn't need all the instruments that Perseverance has since the ExoMars drill unit embeds a miniaturised IR spectrometer for exploration of the borehole, and it could travel right to the places already determined by Perseverance to have the highest probability to get biosignatures.

Or do we have to wait with great expectations until at least 2033, to find out that indeed the returned samples don't contain any biosignatures and then wait again for many years for the results of a next mission with a rover that finally has the capacity to drill down to at least 2 m. ?

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  • $\begingroup$ You could not expect to find biosignatures at every place were you drill down to 2 m. Mars rovers cover very small distances during their lifetime compared to the size of Mars. So you should know a place with a very high probability of biosignatures to land the first ExoMars drill unit. $\endgroup$
    – Uwe
    Commented Dec 10, 2022 at 23:23
  • $\begingroup$ As you point out Exomars is going to do that already. Do we have to wait? Well, yeah, Mars is 34 million miles away at its closest point. $\endgroup$
    – GdD
    Commented Dec 11, 2022 at 0:01
  • $\begingroup$ @Uwe By the time the ExoMars drill unit would arrive in Jezero crater, Perseverance with its instruments should have found the places with the highest probability of biosignatures. $\endgroup$
    – Cornelis
    Commented Dec 11, 2022 at 8:31
  • $\begingroup$ @GdD The ExoMars mission is delayed and will go to Oxia Planum and there are no plans to do a sample return mission there. $\endgroup$
    – Cornelis
    Commented Dec 11, 2022 at 8:35
  • $\begingroup$ Persevance may find a place with high probability of biosignatures only if it was landed at the right place. If it was landed too far away there is no chance to get there with the very limited maximum distance that Persevance may drive. $\endgroup$
    – Uwe
    Commented Dec 11, 2022 at 8:38

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Instead of sending two rovers to Mars, with only one capable of drilling deep/long holes it would have been better to have enabled the existing rover to drill the longer hole.

Two rovers adds significantly more mass cost to the exercise. Enabling a rover to drill longer holes only adds an incremental amount of mass to the rover.

To enable a rover to drill a longer hole, two drill steels would be required, with the second drill steel being able to be connected to the primary drill steel. A holding location would be needed for the second drill steel when its not being used to extend the hole being drilled. Drilling clamps would be required to hold the drill steels during coupling and decoupling and some additional software to enable all this to occur. Then again, instead of only having two drill steels, if mass, space (volume) and cost constraints permitted, more than two drill steels could be used for longer holes. A wire line mechanism and core retriever, as currently used by diamond drilling rigs used for mineral exploration, might be needed to retrieve core if the holes were long.

The technology for this already exists, it would just need to be miniaturized for use on an interplanetary rover.

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  • $\begingroup$ I don't think the existing Perseverance rover could have been enabled to drill much longer holes because it's already packed full with instruments and the sampling and caching system and extra room for a holding location and drilling clamps etc. would be hard to find. $\endgroup$
    – Cornelis
    Commented Dec 11, 2022 at 12:40
  • $\begingroup$ Maybe interesting for you to see how the ExoMars drill unit works: exploration.esa.int/web/mars/-/45796-the-exomars-drill-video $\endgroup$
    – Cornelis
    Commented Dec 11, 2022 at 13:58
  • $\begingroup$ The question to ask is why didn't they do that? Is it incompetence or is there some other reason? How much power would be required to drill deeper with the added resistance? How much more complex and heavier would the probe have been? What other experiments could have been included that weren't because of mass restrictions? And could a heavier probe be dispatched on the same rocket given the exponential nature of the rocket equation and increased mass of EDL requirements? $\endgroup$
    – Slarty
    Commented Dec 12, 2022 at 15:56
  • $\begingroup$ I think it's a good story, but it doesn't excactly answer, and diverts from, the question, so I think it is not a good answer. $\endgroup$
    – Cornelis
    Commented Dec 21, 2022 at 9:56

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