CRUMBLE: An automated computational chemistry package for molecular fragmentation with applications to spaceborne mass spectrometry at icy moons

Aromatic organic compounds have been detected in ice grains ejected in the plume of Enceladus [1-3], demonstrating that they are derived from the subsurface and could be expected in other ocean-bearing icy moons such as Europa. At least two populations of aromatic structures, fragments of high-mass macromolecular and isolated low-mass species, were observed by Cassini’s Cosmic Dust Analyser (CDA [4]) during hypervelocity impacts of ice grains. Interpretations of CDA mass spectra have relied on laboratory analogue experiments [5], but theoretical insights into molecular impact fragmentation through quantum chemistry would add an additional technique to the toolbox of habitability-investigating missions at icy ocean worlds, such as Europa Clipper and ESA’s L4 mission to Enceladus [6].

A common challenge faced in computational chemistry investigations is the laborious construction of the potential energy surface (PES) when exploring the dissociation of a molecule under space conditions. Many molecular fragmentation pathways can be accessed in energetic processes, e.g. radiolytic chemistry and impact ionisation of ice grains onto spaceborne mass spectrometers at hypervelocity. Previous theoretical work into understanding impact ionisation mass spectra has been conducted by tedious exploration of the full fragmentation space [7]. To the best of our knowledge, there is no general-purpose method currently available for systematically surveying the full fragmentation space of a given organic molecule with quantum chemistry.

Here, we introduce the Chemical Rupture Understanding through Molecular Bonding and Liberation Energetics (CRUMBLE) package, in which we compute the dissociation energies using a graph theoretical approach for enumerating all binary fragmentation channels of a given molecule. The fragment channels are ranked by the number of bonds broken or formed, or the thermodynamic dissociation energy. Fragment structures calculated at a given quantum chemical method are stored in a library that is queried to reduce the computational expense associated with future runs. With representative examples, we demonstrate that CRUMBLE enables researchers to quickly locate minima in the fragmentation space of molecules and generate valuable quantum chemical data for each fragment and its isomers to aid in mass spectrometric investigation. This package can be applied to many environments in space: Cassini, Europa Clipper, and possibly ESA’s L4 mission have sampled or will sample organic-bearing ice grains at icy ocean moons, and JAXA’s DESTINY+ mission will sample dust emitted by the near-Earth asteroids Phaethon and Apophis at hypervelocities with the DESTINY+ Dust Analyser (DDA [8]). Beyond spaceborne mass spectrometry, CRUMBLE is broadly applicable to any context in which the fragmentation space of a molecule is explored, including the dissociation of molecules in the interstellar medium and protoplanetary disks, and the top-down processing of large molecules into smaller fragments in energetic astrophysical environments.   

References:

[1] Postberg, F. et al. Nature, 2018. 558(7711): p. 564-568.

[2] Khawaja, N. et al., Monthly Notices of the Royal Astronomical Society, 2019. 489(4): p. 5231-5243.

[3] Khawaja, N. et al., Nature Astronomy, 2025. 9: p. 1662-1671

[4] Srama, R. et al., Space Science Reviews, 2004. 114(1-4): p. 465-518.

[5] Klenner, F. et al. Rapid Communications in Mass Spectrometry, 2019. 33(22): p. 1751-1760.

[6] Helbert, J. et al. The Mission to Enceladus – The ESA L4 mission. EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1307.

[7] O’Sullivan, T.R. et al., ACS Earth and Space Chemistry, 2026. 10(4), p. 1033-1046.

[8] Simolka, J. et al. Philosophical Transactions of the Royal Society A, 2024. 382(2273): 20230199.