Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

A Martian origin for the Mars Trojan asteroids


Seven of the nine known Mars Trojan asteroids belong to an orbital cluster1,2 named after its largest member, (5261) Eureka. Eureka is probably the progenitor of the whole cluster, which formed at least 1 Gyr ago3. It has been suggested3 that the thermal YORP (Yarkovsky–O'Keefe–Radzievskii–Paddack) effect spun up Eureka, resulting in fragments being ejected by the rotational-fission mechanism. Eureka’s spectrum exhibits a broad and deep absorption band around 1 μm, indicating an olivine-rich composition4. Here we show evidence that the Trojan Eureka cluster progenitor could have originated as impact debris excavated from the Martian mantle. We present new near-infrared observations of two Trojans ((311999) 2007 NS2 and (385250) 2001 DH47) and find that both exhibit an olivine-rich reflectance spectrum similar to Eureka’s. These measurements confirm that the progenitor of the cluster has an achondritic composition4. Olivine-rich reflectance spectra are rare amongst asteroids5 but are seen around the largest basins on Mars6. They are also consistent with some Martian meteorites (for example, Chassigny7) and with the material comprising much of the Martian mantle8,9. Using numerical simulations, we show that the Mars Trojans are more likely to be impact ejecta from Mars than captured olivine-rich asteroids transported from the main belt. This result directly links specific asteroids to debris from the forming planets.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: | Reflectance spectra comparison.
Figure 2: Impact ejecta dispersal.
Figure 3: Production rate of Mars Trojans.

Similar content being viewed by others


  1. Christou, A. et al. New Martian Trojans and an update on the Eureka cluster. In European Planetary Science Congress Abstracts Vol. 9, id. EPSC2014-696 (European Planetary Science Congress, 2014).

  2. de la Fuente, C. & de la Fuente, R. Three new stable L5 Mars Trojans. Mon. Not. R. Astron. Soc. 432, L31–L35 (2013).

    Article  ADS  Google Scholar 

  3. Cuk, M. Christou, A. A. & Hamilton, D. P. Yarkovsky-driven spreading of the Eureka family of Mars Trojans. Icarus 252, 339–346 (2015).

    Article  ADS  Google Scholar 

  4. Rivkin, A. S. et al. Composition of the L5 Mars Trojans: neighbors, not siblings. Icarus 192, 434–441 (2007).

    Article  ADS  Google Scholar 

  5. DeMeo, F. E. & Carry, B. The taxonomic distribution of asteroids from multi-filter all-sky photometric surveys. Icarus 226, 723–741 (2013).

    Article  ADS  Google Scholar 

  6. Ehlmann, B. L. & Edwards C. S. Mineralogy of the Martian surface. Annu. Rev. Earth Planet. Sci. 42, 291–315 (2014).

    Article  ADS  Google Scholar 

  7. McSween, H. Y. SNC meteorites—clues to Martian petrologic evolution? Rev. Geophys. 23, 391–416 (1985).

    Article  ADS  Google Scholar 

  8. Bertka, C. M. & Fei, Y. Mineralogy of the Martian interior up to core–mantle boundary pressures. J. Geophys. Res. 102, 5251–5264 (1997).

    Article  ADS  Google Scholar 

  9. Zuber, M. T. The crust and mantle of Mars. Nature 412, 220–227 (2001).

    Article  ADS  Google Scholar 

  10. Borisov, G. et al. The olivine-dominated composition of the Eureka family of Mars Trojan asteroids. Mon. Not. R. Astron. Soc. 466, 489–495 (2017).

    Article  ADS  Google Scholar 

  11. DeMeo, F. E., Binzel, R. P., Slivan, S. M. & Bus, S. J. An extension of the Bus asteroid taxonomy into the near-infrared. Icarus 202, 160–180 (2009).

    Article  ADS  Google Scholar 

  12. Shkuratov, Y., Starukhina, L., Hoffmann, H. & Arnold, G. A model of spectral albedo of particulate surfaces: implications for optical properties of the Moon. Icarus 137, 235–246 (1999).

    Article  ADS  Google Scholar 

  13. Burt, B. J., DeMeo, F. E. & Binzel, R. P. Origin and mineralogy of olivine-dominated near-Earth asteroids. In American Astronomical Society Meeting Abstracts Vol. 224, abstr. 321.08 (American Astronomical Society, 2014).

  14. Mustard, J. F. et al. Composition, morphology, and stratigraphy of Noachian crust around the Isidis basin. J. Geophys. Res. 114, E00D12 (2009).

    Article  Google Scholar 

  15. Murray, C. D. & Dermott, S. F. Solar System Dynamics (Cambridge Univ. Press, 1999).

    MATH  Google Scholar 

  16. Scholl, H., Marzari, F. & Tricarico, P. Dynamics of Mars Trojans. Icarus 175, 397–408 (2005).

    Article  ADS  Google Scholar 

  17. Chambers, J. E. Make more terrestrial planets. Icarus 152, 205–224 (2001).

    Article  ADS  Google Scholar 

  18. Brasser, R. & Lehto, H. J. The role of secular resonances on trojans of the terrestrial planets. Mon. Not. R. Astron. Soc. 334, 241–247 (2002).

    Article  ADS  Google Scholar 

  19. Walsh, K. J., Morbidelli, A., Raymond, S. N., O’Brien, D. P. & Mandell, A. M. A low mass for Mars from Jupiter's early gas-driven migration. Nature 475, 206–209 (2011).

    Article  ADS  Google Scholar 

  20. Jacobson, S. A. & Morbidelli, A. Lunar and terrestrial planet formation in the Grand Tack scenario. Phil. Trans. R. Soc. A 372, 20130174 (2014).

    Article  ADS  Google Scholar 

  21. Marinova, M. M., Aharonson, O. & Asphaug, E. Mega-impact formation of the Mars hemispheric dichotomy. Nature 453, 1216–1219 (2008).

    Article  ADS  Google Scholar 

  22. Leinhardt, Z. M. & Stewart, S. T. Collisions between gravity-dominated bodies. I. Outcome regimes and scaling laws. Astrophys. J. 745, 79 (2012).

    Article  ADS  Google Scholar 

  23. Nugent, C. R. et al. NEOWISE reactivation mission year one: preliminary asteroid diameters and albedos. Astrophys. J. 814, 117 (2015).

    Article  ADS  Google Scholar 

  24. McEachern, F. M., Cuk, M. & Stewart, S. T. Dynamical evolution of the Hungaria asteroids. Icarus 210, 644–654 (2010).

    Article  ADS  Google Scholar 

  25. Cuk, M. Chronology and sources of lunar impact bombardment. Icarus 218, 69–79 (2012)

    Article  ADS  Google Scholar 

  26. Bottke, W. F. et al. An Archaean heavy bombardment from a destabilized extension of the asteroid belt. Nature 485, 78–81 (2012)

    Article  ADS  Google Scholar 

  27. Bottke, W. F. et al. Dating the Moon-forming impact event with asteroidal meteorites. Science 348, 321–323 (2015).

    Article  ADS  Google Scholar 

  28. Nyquist, L. E. et al. Ages and geologic histories of Martian meteorites. Space Sci. Rev. 96, 105–164 (2001).

    Article  ADS  Google Scholar 

  29. Jacobson, S. A. et al. There’s too much mantle material in the asteroid belt. In 47th Lunar and Planetary Science Conference 1895 (Lunar and Planetary Institute, 2016).

  30. Polishook, D. et al. Observations of “fresh” and weathered surfaces on asteroid pairs and their implications on the rotational-fission mechanism. Icarus 233, 9–26 (2014).

    Article  ADS  Google Scholar 

  31. Wisdom, J. & Holman, M. Symplectic maps for the n-body problem. Astron. J. 102, 1528–1538 (1991).

    Article  ADS  Google Scholar 

  32. Levison, H. F. & Duncan, M. J. Symplectically integrating close encounters with the Sun. Astron. J. 120, 2117–2123 (2000).

    Article  ADS  Google Scholar 

  33. Rivkin, A. S., Brown, R. H., Trilling, D. E., Bell, J. F. & Plassmann, J. H. Near-infrared spectrophotometry of Phobos and Deimos. Icarus 156, 64–75 (2002).

    Article  ADS  Google Scholar 

  34. Citron, R. I., Genda, H. & Ida, S. Formation of Phobos and Deimos via a giant impact. Icarus 252, 334–338 (2015).

    Article  ADS  Google Scholar 

  35. Marinova, M. M., Aharonson, O. & Asphaug, E. Geophysical consequences of planetary-scale impacts into a Mars-like planet. Icarus 211, 960–985 (2011).

    Article  ADS  Google Scholar 

  36. Canup, R. M. & Asphaug, E. Origin of the Moon in a giant impact near the end of the Earth’s formation. Nature 412, 708–712 (2001).

    Article  ADS  Google Scholar 

Download references


We thank F. DeMeo and B. Burt for their help with spectral analysis of olivine asteroids, and J. Mustard for providing CRISM reflectance spectra of Mars. D.P. is grateful to the Ministry of Science, Technology and Space of the Israeli government for their Ramon fellowship for post-docs. S.A.J. and A.M. were supported by the European Research Council Advanced Grant ‘ACCRETE’ (contract number 290568). O.A. acknowledges support from the Helen Kimmel Center for Planetary Science, the Minerva Center for Life Under Extreme Planetary Conditions and the I-CORE Program of the Planning and Budgeting Committee of the Council for Higher Education and the Israeli Science Foundation (Center No. 1829/12). Observations for this study were performed in Hawaii. We are most fortunate to have had the opportunity to conduct observations from the Mauna Kea Observatory, and we thank the NASA Infrared Telescope Facility staff for their continuous help.

Author information

Authors and Affiliations



D.P. and S.A.J. led the project and wrote the manuscript. D.P. ran the observations, reduction and analysis of the spectral data. S.A.J. wrote the dynamical simulations and analysed their results. All authors participated in the interpretation of the results.

Corresponding author

Correspondence to D. Polishook.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Table 1 and Supplementary References (PDF 176 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Polishook, D., Jacobson, S., Morbidelli, A. et al. A Martian origin for the Mars Trojan asteroids. Nat Astron 1, 0179 (2017).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing