Welcome LPSC '26 Attendees!

We are enabling an entirely revamped MSR architecture.

The Drastic Architecture Improvements

Our in situ sterilization technology is the key to the whole thing. Because samples arrive at Earth already sterilized, a failure of containment is no longer a failure of planetary protection. This single principle reshapes the entire return architecture:

• The Orbiting Sample container (OS) still serves as the primary containment vessel, but its job changes from "never break open under any circumstances" to "hold and protect samples during transit" (it can be lighter-weight with less crush core)
• The lighter OS means a smaller (well, it's also more advanced) Mars Ascent Vehicle (MAV)
• The lighter MAV means the lander that delivers it can fit within the mass/volume envelope of a skycrane lander (a Curiosity/Perseverance-class lander without the wheels, suspension, mast, etc.)
• The Capture, Containment and Return System (CCRS) drops from roughly 625 kg to on the order of 100-200 kg because it no longer needs a super-complicated, quad-redundant containment system, and carries no Earth Entry Vehicle (EEV)
• The Earth Return Orbiter (ERO) will park in lunar orbit and rendezvous with a commercial EEV, which uses a parachute during the entry process
  • Previous MSR architectures could not accept the risk of parachute recovery system, because even a less-than-one-in-a-thousand chance of failure was unacceptable when containment was the only line of planetary protection defense. So the previous EEV was designed for an 1,800-g hard impact, and was part of the CCRS
  • With sterilized samples, this is no longer an issue (say it with me: a failure of containment is not a failure of planetary protection!)
  • This is actually a potential boon to science, because the impact is so much more gentle that there will be less crushing of rock samples in their tubes (which had been expected)
• The Sample Receiving Facility is no longer necessary, and samples can be distributed to laboratories immediately.

The Details:

A sterilization approach for backward planetary protection of Mars Sample Return (MSR) samples using a ¹³⁷Cs gamma source integrated into the OS. The radioisotope is brought from Earth; sterilization occurs in situ during the ~3-year Earth return transit, not at the SRF (which becomes optional). Our goal is to support the Break the Chain at Mars mission concept emerging from NASA's Jet Propulsion Laboratory [1], and provide a complementary menu of radioisotope sterilization solutions [2] by enhancing the statistical argument JPL is putting forth in that emerging architecture. We are trying to save Mars Sample Return.

Technical specifications:

• Source: ¹³⁷Cs (662 keV gamma)
• Reference dose: 100 kGy
• Dose rate: ~1 mGy/s (delivered over ~3 years during transit)
• Samples sterilized to a Sterilization Assurance Level (SAL) of 10⁻¹² - 10⁻²⁴ before entering Earth's biosphere

This approach allows simplified planetary protection processes to exist for the return phase of the mission, and augments the Break the Chain at Mars approach. The mission becomes an unrestricted sample return mission.

The trade-off

Any sterilization method which inactivates potential organisms will also affect sample science to some degree. Gamma radiation at 100 kGy is excellent for microbial reduction, but causes organic radiolysis, water radiolysis in hydrous phases, and defect center creation. The central question is whether planetary protection can be achieved while preserving sufficient science value. The science assessment in this entry uses 100 kGy as the reference dose; however, the architecture supports configurable doses from 25 kGy (FDA sterilization standard) up to 300 kGy depending on the risk posture selected.

The impact on MSR science objectives is assessed across 280 technique × sub-objective intersections (76 unique analytical techniques × 19 MSR science sub-objectives) in our Gamma Sensitivity Workbook [3] (best to download a copy and reference sheet 3), and is substantiated by a technical report [4].

The Role of the Evidence Ledger

This Evidence Ledger concept is step one of a three-step trajectory: (1) Evidence Ledger to collect expert feedback on individual claims, (2) a preliminary assurance case document with structured arguments for auditability and peer review, and (3) a formal version-controlled assurance case report incorporating expert verdicts as a living document to be presented to NASA at the end of a potential Phase II SBIR.

Today the claims here are mainly science-related. We are trying to capture feedback from the science community about the effect of gamma radiation on sample science and on gamma sterilization effectiveness, in an MSR context. Please participate! We are moving forward quickly and need to collect community feedback. Some of your colleagues may be participating in workshops on this topic, but this collection mechanism is being operated in parallel. Help us by criticizing our approach and challenging our thinking. We want to hear it. Now is the time. Of course, supportive comments are allowed, too.

Changelog

Tags

MSR, planetary protection, gamma sterilization, mars sample return, microbiology, astrobiology