Skip to main content Accessibility help

Exporting terrestrial life out of the Solar System with gravitational slingshots of Earthgrazing bodies

  • Amir Siraj (a1) and Abraham Loeb (a1)


Exporting terrestrial life out of the Solar System requires a process that both embeds microbes in boulders and ejects those boulders out of the Solar System. We explore the possibility that Earthgrazing long-period comets (LPCs) and interstellar objects (ISOs) could export life from Earth by collecting microbes from the atmosphere and receiving a gravitational slingshot effect from the Earth. We estimate the total number of exportation events over the lifetime of the Earth to be ~1–10 for LPCs and ~1–50 for ISOs. If life existed above an altitude of 100 km, then the number is dramatically increased up to ~105 exportation events over Earth's lifetime.


Corresponding author

Author for correspondence: Amir Siraj, E-mail:


Hide All
Bailey, ME and Stagg, CR (1988) Solar obliquity induced by planet nine. Monthly Notices of the Royal Astronomical Society 152, 126.
Belbruno, E, Moro-Martin, A, Malhotra, R and Savransky, D (2012) Chaotic Exchange of Solid Material Between Planetary Systems. Astrobiology 12, 754.
Burrows, SM, Elbert, W, Lawrence, MG and Pöschl, U (2009) Bacteria in the global atmosphere – Part 1: Review and synthesis of literature data for different ecosystems. Atmospheric Chemistry and Physics 9, 9236.
Collins, GS, Jay, HM and Marcus, RA (2010) Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth. Meteoritics & Planetary Science 40, 817.
Deguchi, S, Tsuji, K and Horikoshi, Koki (2011) Microbial growth at hyperaccelerations up to 403, 627 × g. Proceedings of the National Academy of Sciences of the United States of America 108, 7997.
Do, A, Tucker, MA and Tonry, J (2018) Interstellar interlopers: number density and origin of 'Oumuamua-like objects. The Astrophysical Journal 855, L10.
Fernandez, JA and Sosa, A (2012) Magnitude and size distribution of long-period comets in Earth-crossing or approaching orbits. Monthly Notices of the Royal Astronomical Society 423, 1674.
Francis, PJ (2005) The demographics of long-period Comets. The Astrophysical Journal 635, 1348.
Fritz, J, Artemieva, N and Greshake, A (2005) Ejection of Martian meteorites. Meteoritics & Planetary Science 40, 1393.
Ginsburg, I, Lingam, M and Loeb, A (2018) Galactic Panspermia. The Astrophysical Journal 868, 1.
Guzik, M, Drahus, M, Rusek, K, Waniak, W, Cannizzaro, G and Pastor-Marazuela, I (2019) Interstellar comet C/2019 Q4 (Borisov) (arXiv:1909.05851).
Imshenetsky, AA, Lysenko, SV and Kazakov, GA (1978) Upper boundary of the biosphere. Applied and Environmental Microbiology 35, 1.
Lingam, M and Loeb, A (2018) Implications of captured interstellar objects for Panspermia and extraterrestrial life. The Astronomical Journal 156,193.
Mastrapa, RME, Glanzberg, H, Head, JN, Melosh, J and Nicholson, WL (2001) Survival of bacteria exposed to extreme acceleration: implications for panspermia. Earth and Planetary Science Letters 189, 1.
Meech, KJ, Weryk, R, Micheli, M, Kleyna, JT, Hainaut, OR, Jedicke, R, Wainscoat, RJ, Chambers, KC, Keane, JV, Petric, A, Denneau, L, Magnier, E, Berger, T, Huber, ME, Flewelling, H, Waters, C, Schunova-Lilly, E and Chastel, S (2017) A brief visit from a red and extremely elongated interstellar asteroid. Nature 552, 378.
Micheli, M, Farnocchia, D, Meech, KJ, Buie, MW, Hainaut, OR, Prialnik, D, Schörghofer, N, Weaver, HA, Chodas, PW, Kleyna, JT, Weryk, R, Wainscoat, RJ, Ebeling, H, Keane, JV, Chambers, KC, Koschny, D and Petropoulos, AE (2018) Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature 559, 223.
Mileikowsky, C, Cucinotta, FA, Wilson, JW, Gladman, B, Horneck, G, Lindegren, L, Melosh, J, Rickman, H, Valtonen, M and Zheng, JQ (2000) Natural transfer of viable microbes in space: 1. From Mars to Earth and Earth to Mars. Icarus 145, 2.
Register, PJ, Mathias, DL and Wheeler, LF (2017) Asteroid fragmentation approaches for modeling atmospheric energy deposition. Icarus 284, 157.
Rein, H and Liu, S-F (2012) REBOUND: An open-source multi-purpose N-body code for collisional dynamics. Astronomy & Astrophysics 537, A128.
Rein, H and Spiegel, DS (2014) IAS15: A fast, adaptive, high-order integrator for gravitational dynamics, accurate to machine precision over a billion orbits. Monthly Notices of the Royal Astronomical Society 446, 1424.
Siraj, A and Loeb, A (2019a) Discovery of a meteor of interstellar origin, submitted to The Astrophysical Journal Letters.
Siraj, A and Loeb, A (2019b) An argument for a kilometer-scale nucleus of C/2019 Q4. Research Notes of the American Astronomical Society 3, 132.
Smith, DJ (2013) Microbes in the Upper Atmosphere and Unique Opportunities for Astrobiology Research. Astrobiology 13, 981.
Trilling, DE, Mommert, M, Hora, JL, Farnocchia, D, Chodas, P, Giorgini, J, Smith, HA, Carey, S, Lisse, CM, Werner, A, McNeill, A, Chesley, SR, Emery, JP, Fazio, G, Fernandez, YR, Harris, A, Marengo, M, Mueller, M, Roegge, A, Smith, N, Weaver, HA, Meech, K and Micheli, M (2018) Spitzer observations of interstellar object 1I/'Oumuamua. The Astronomical Journal 156, 261.
Vokrouhlicky, D, Nesvorny, D and Dones, L (2019) Origin and evolution of long-period comets. The Astronomical Journal 157, 5.
Wainwright, M, Weber, PK, Smith, JB, Hutcheon, ID, Klyce, B, Wickramasinghe, NC, Narlikar, JV and Rajaratnam, P (2004) Studies on bacteria-like particles sampled from the stratosphere. Aerobiologia 20, 237.
Weissman, PR (1990) Global catastrophes in earth history. An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality, Vol. 247. Geological Society of America, Boulder, pp. 171–180.
Weissman, PR (2007) The cometary impactor flux at the Earth. Proceedings IAU Symposium No. 236, Praha, Vol. 156, p. 329.
Wesson, PS (2010) Panspermia, past and present: astrophysical and biophysical conditions for the dissemination of life in space. Space Science Reviews 156, 329.
Wickramasinghe, C (2010) The astrobiological case for our cosmic ancestry. Space Science Reviews 9, 119.


Exporting terrestrial life out of the Solar System with gravitational slingshots of Earthgrazing bodies

  • Amir Siraj (a1) and Abraham Loeb (a1)


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed