Telescopic measurements of asteroids’ colours rarely match laboratory reflectance spectra of meteorites owing to a ‘space weathering’1,2 process that rapidly3 reddens asteroid surfaces in less than 106 years. ‘Unweathered’ asteroids (those having spectra matching the most commonly falling ordinary chondrite meteorites), however, are seen among small bodies the orbits of which cross inside Mars and the Earth. Various explanations have been proposed for the origin of these fresh surface colours, ranging from collisions4 to planetary encounters5. Less reddened asteroids seem to cross most deeply into the terrestrial planet region, strengthening6 the evidence for the planetary-encounter theory5, but encounter details within 106 years remain to be shown. Here we report that asteroids displaying unweathered spectra (so-called ‘Q-types’7) have experienced orbital intersections closer than the Earth–Moon distance within the past 5 × 105 years. These Q-type asteroids are not currently found among asteroids showing no evidence of recent close planetary encounters. Our results substantiate previous work5: tidal stress8, strong enough to disturb and expose unweathered surface grains, is the most likely dominant short-term asteroid resurfacing process. Although the seismology details are yet to be worked out, the identification of rapid physical processes that can produce both fresh and weathered asteroid surfaces resolves the decades-long9 puzzle of the difference in colour of asteroids and meteorites.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Clark, B. E., Hapke, B., Pieters, C. & Britt, D. in Asteroids III (eds Bottke, W. F., Cellino, A., Paolicchi, P. & Binzel, R. P.) 585–589 (University of Arizona Press, 2002)
Chapman, C. R. Space weathering of asteroid surfaces. Annu. Rev. Earth Planet. Sci. 32, 539–567 (2004)
Vernazza, P., Binzel, R. P., Rossi, A., Fulchignoni, M. & Birlan, M. Solar wind as the origin of rapid weathering of asteroid surfaces. Nature 458, 993–995 (2009)
Binzel, R. P. et al. Observed spectral properties of near-Earth objects: results for population distribution, source regions, and space weathering processes. Icarus 170, 259–294 (2004)
Nesvorný, D., Jedicke, R., Whiteley, R. J. & Ivezic, Z. Evidence for asteroid space weathering from the Sloan Digital Sky Survey. Icarus 173, 132–152 (2005)
Marchi, S., Magrin, S., Nesvorný, D., Paolicchi, P. & Lazzarin, M. A spectral slope versus perihelion distance correlation for planet-crossing asteroids. Mon. Not. R. Astron. Soc. 368, 39–42 (2006)
McFadden, L. A., Gaffey, M. J. & McCord, T. B. Near-earth asteroids—possible sources from reflectance spectroscopy. Science 229, 160–163 (1985)
Richardson, D. C., Bottke, W. F. & Love, S. G. Tidal distortion and disruption of Earth-crossing asteroids. Icarus 134, 47–76 (1998)
Wetherill, G. W. & Chapman, C. R. in Meteorites and the Early Solar System (eds Kerridge, J. F. & Matthews, M. S.) 35–67 (University of Arizona Press, 1988)
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)
Bonanno, C. An analytical approximation for the MOID and its consequences. Astron. Astrophys. 360, 411–416 (2000)
Wisdom, J. & Holman, M. Symplectic maps for the n-body problem. Astron. J. 102, 1528–1538 (1991)
Levison, H. F. & Duncan, M. J. The long-term dynamical behavior of short-period comets. Icarus 108, 18–36 (1994)
Zellner, B., Tholen, D. J. & Tedesco, E. F. The eight-color asteroid survey: results for 589 minor planets. Icarus 61, 355–416 (1985)
Bus, S. J. & Binzel, R. P. Phase II of the small main-belt asteroid spectroscopic survey. Icarus 158, 106–145 (2002)
Lazzaro, D. et al. S3OS2: the visible spectroscopic survey of 820 asteroids. Icarus 172, 179–220 (2004)
Murchie, S. R. et al. Color variations on Eros from NEAR multispectral imaging. Icarus 155, 145–168 (2002)
Saito, J. et al. Detailed images of asteroid 25143 Itokawa from Hayabusa. Science 312, 1341–1344 (2006)
Holsapple, K. A. & Michel, P. Tidal disruptions: a continuum theory for solid bodies. Icarus 183, 331–348 (2006)
Stuart, J. S. & Binzel, R. P. Bias-corrected population, size distribution, and impact hazard for the near-Earth objects. Icarus 170, 295–311 (2004)
Grady, M. M. Catalogue of Meteorites 689 (Cambridge University, 2000)
Trombka, J. I. et al. The elemental composition of asteroid 433 Eros: results of the NEAR-Shoemaker X-ray spectrometer. Science 289, 2101–2105 (2000)
Scheeres, D. J. The dynamical evolution of uniformly rotating asteroids subject to YORP. Icarus 188, 430–450 (2007)
Binzel, R. P. et al. Spectral properties and composition of potentially hazardous asteroid (99942) Apophis. Icarus 200, 480–485 (2009)
Scheeres, D. J. et al. Abrupt alteration of asteroid 2004 MN4’s spin state during its 2029 Earth flyby. Icarus 178, 281–283 (2005)
Gaffey, M. J., Cloutis, E. A., Kelly, M. S. & Reed, K. L. in Asteroids III (eds Bottke, W. F., Cellino, A., Paolicchi, P. & Binzel, R. P.) 183–204 (University of Arizona Press, 2002)
Burbine, T. H., McCoy, T. J., Jarosewich, E. & Sunshine, J. M. Deriving asteroid mineralogies from reflectance spectra: implications for the Muses-C target asteroid. Antarct. Meteor. Res. 16, 185–195 (2003)
Strazzulla, G. et al. Spectral alteration of the meteorite Epinal (H5) induced by heavy ion irradiation: a simulation of space weathering effects on near-Earth asteroids. Icarus 174, 31–35 (2005)
R.P.B. is a Chercheur Associé at the Observatoire de Paris IMCCE and thanks IMCCE and LESIA for their collaboration and hospitality during the initiation of this analysis. We thank C. Chapman, B. Clark, D. Richardson and D. Nesvorný for their constructive reviews and comments. Observations reported here were obtained at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. F.E.D. acknowledges funding from the Fulbright Program. This material is based upon work supported by the National Science Foundation under grant 0506716 and NASA under grant NAG5-12355. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or NASA.
Author Contributions R.P.B. and A.T.T. served as principal investigators for a joint observing programme to acquire the near-infrared spectral data. Most data were acquired by R.P.B., C.A.T. and F.E.D., while F.E.D. performed most of the processing and taxonomic evaluation. Processing routines were developed by S.J.B., A.S.R. and R.P.B. The scientific analysis was directed by R.P.B. with the first stages performed by S.M. with input from M.B. and P.V. A.M. performed all of the orbital integrations. R.P.B. and A.M. worked jointly to draft the manuscript with all authors reviewing and contributing to its final form.
The authors declare no competing financial interests.
About this article
Cite this article
Binzel, R., Morbidelli, A., Merouane, S. et al. Earth encounters as the origin of fresh surfaces on near-Earth asteroids. Nature 463, 331–334 (2010). https://doi.org/10.1038/nature08709
The Astronomical Journal (2020)
Astronomy & Astrophysics (2020)
Monthly Notices of the Royal Astronomical Society (2020)
Acta Astronautica (2020)