Near-Earth asteroid 2012 TC4 observing campaign

Results from a global planetary defense exercise

Vishnu Reddy, Michael S. Kelley, Davide Farnocchia, William H. Ryan, Cristina A. Thomas, Lance A.M. Benner, Jessie Dotson, Marco Micheli, Melissa J. Brucker, Schelte J. Bus, Marina Brozovic, Lorien Wheeler, Viqar Abbasi, James M. Bauer, Amber Bonsall, Zarah L. Brown, Michael W. Busch, Paul Chodas, Young Jun Choi, Nicolas Erasmus & 49 others Kelly E. Fast, John P. Faucher, Rachel B. Fernandes, Frank D. Ghigo, David G. Gilbank, Jon D. Giorgini, Annika Gustafsson, Olivier Hainaut, Walter M. Harris, Joseph S. Jao, Lindley S. Johnson, Theodore Kareta, Myung Jin Kim, Detlef Koschny, Emily A. Kramer, Rob R. Landis, Denis G. Laurin, Jeffrey A. Larsen, Clement G. Lee, Cassandra Lejoly, Tim Lister, Robert McMillan, Joseph R. Masiero, Donovan Mathias, Michael Mommert, Hong Kyu Moon, Nicholas A. Moskovitz, Shantanu P. Naidu, Ravi Teja Nallapu, Haris Khan Niazi, John W. Noonan, David Polishook, Eileen V. Ryan, Lauren Schatz, James V. Scotti, Benjamin Sharkey, Boris M. Shustov, Amanda A. Sickafoose, Marc A. Silva, Martin A. Slade, Lindsay R. Slick, Lawrence G. Snedeker, Alessandra Springmann, David Tholen, David E Trilling, Alberto Q. Vodniza, Richard Wainscoat, Robert Weryk, Makoto Yoshikawa

Research output: Contribution to journalArticle

Abstract

Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characterize smaller objects. In an effort to test our preparedness to respond to a potential NEO impact threat, we conducted a community-led global planetary defense exercise with support from the NASA Planetary Defense Coordination Office. The target of our exercise was 2012 TC4, the ~10 m diameter asteroid that made a close pass by the Earth on 2017 October 12 at a distance of about 50,000 km. The goal of the TC4 observing campaign was to recover, track, and characterize 2012 TC4 as a hypothetical impactor in order to exercise the global planetary defense system involving observations, modeling, prediction, and communication. We made three attempts with the Very Large Telescope (VLT) on 2017 July 27, 31 and on 2017 August 5 and recovered 2012 TC4 within its ephemeris uncertainty at 2.2 arcmin from the nominal prediction. At visual magnitude V = 27, the recovery of 2012 TC4 is the faintest NEA detection thus far. If an impact during the 2017 close approach had been possible based on the 2012 astrometric data, these recovery observations would have been sufficient to confirm or rule out the impact. The first automatic detection by a survey (Pan-STARRS1) was on September 25, which is the earliest that 2012 TC4 would have been discovered in survey mode, if it had not been discovered in 2012. We characterized 2012 TC4 using photometry, spectroscopy and radar techniques. Based on photometric observations, we determined a rotation period of 12.2 min with an amplitude of 0.9 magnitudes. An additional lower amplitude period was detected, indicating that 2012 TC4 was in a state of non-principal axis rotation. The combined visible and near-infrared spectrum puts it in the taxonomic X-class. Radar images at 1.875 m resolution placed only a few range pixels on the asteroid, reveal an angular, asymmetric, and elongated shape, and establish that 2012 TC4 is less than 20 m on its long axis. We estimate a circular polarization ratio of 0.57 + -0.08 that is relatively high among NEAs observed to date by radar. We also performed a probabilistic impact risk assessment exercise for hypothetical impactors based on the 2012 TC4 observing campaign. This exercise was performed as part of ongoing efforts to advance effective impact risk models and assessment processes for planetary defense. The 2012 TC4 close approach provided a valuable opportunity to test the application of these methods using realistically evolving observational data to define the modeling inputs. To this end, risk assessments were calculated at several epochs before and during the close approach, incorporating new information about 2012 TC4 as it became available. Two size ranges were assessed—one smaller size range (H = 26.7) similar to the actual 2012 TC4, and one larger size range (H = 21.9) to produce a greater-damage scenario for risk assessment. Across the epochs, we found that only irons caused significant damage for smaller size. For the larger size case, however, hydrous stones caused the greatest damage, anhydrous stones caused the least damage, and irons caused moderate damage. We note that the extent of damage depends on composition in different size regimes and, after astrometry, size is the most important physical property to determine for an incoming object.

Original languageEnglish (US)
Pages (from-to)133-150
Number of pages18
JournalIcarus
Volume326
DOIs
StatePublished - Jul 1 2019

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physical exercise
asteroids
asteroid
damage
near Earth objects
risk assessment
range size
radar
impactors
recovery
iron
time measurement
rocks
mass extinction
prediction
astrometry
disasters
modeling
circular polarization
predictions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Reddy, V., Kelley, M. S., Farnocchia, D., Ryan, W. H., Thomas, C. A., Benner, L. A. M., ... Yoshikawa, M. (2019). Near-Earth asteroid 2012 TC4 observing campaign: Results from a global planetary defense exercise. Icarus, 326, 133-150. https://doi.org/10.1016/j.icarus.2019.02.018

Near-Earth asteroid 2012 TC4 observing campaign : Results from a global planetary defense exercise. / Reddy, Vishnu; Kelley, Michael S.; Farnocchia, Davide; Ryan, William H.; Thomas, Cristina A.; Benner, Lance A.M.; Dotson, Jessie; Micheli, Marco; Brucker, Melissa J.; Bus, Schelte J.; Brozovic, Marina; Wheeler, Lorien; Abbasi, Viqar; Bauer, James M.; Bonsall, Amber; Brown, Zarah L.; Busch, Michael W.; Chodas, Paul; Choi, Young Jun; Erasmus, Nicolas; Fast, Kelly E.; Faucher, John P.; Fernandes, Rachel B.; Ghigo, Frank D.; Gilbank, David G.; Giorgini, Jon D.; Gustafsson, Annika; Hainaut, Olivier; Harris, Walter M.; Jao, Joseph S.; Johnson, Lindley S.; Kareta, Theodore; Kim, Myung Jin; Koschny, Detlef; Kramer, Emily A.; Landis, Rob R.; Laurin, Denis G.; Larsen, Jeffrey A.; Lee, Clement G.; Lejoly, Cassandra; Lister, Tim; McMillan, Robert; Masiero, Joseph R.; Mathias, Donovan; Mommert, Michael; Moon, Hong Kyu; Moskovitz, Nicholas A.; Naidu, Shantanu P.; Nallapu, Ravi Teja; Niazi, Haris Khan; Noonan, John W.; Polishook, David; Ryan, Eileen V.; Schatz, Lauren; Scotti, James V.; Sharkey, Benjamin; Shustov, Boris M.; Sickafoose, Amanda A.; Silva, Marc A.; Slade, Martin A.; Slick, Lindsay R.; Snedeker, Lawrence G.; Springmann, Alessandra; Tholen, David; Trilling, David E; Vodniza, Alberto Q.; Wainscoat, Richard; Weryk, Robert; Yoshikawa, Makoto.

In: Icarus, Vol. 326, 01.07.2019, p. 133-150.

Research output: Contribution to journalArticle

Reddy, V, Kelley, MS, Farnocchia, D, Ryan, WH, Thomas, CA, Benner, LAM, Dotson, J, Micheli, M, Brucker, MJ, Bus, SJ, Brozovic, M, Wheeler, L, Abbasi, V, Bauer, JM, Bonsall, A, Brown, ZL, Busch, MW, Chodas, P, Choi, YJ, Erasmus, N, Fast, KE, Faucher, JP, Fernandes, RB, Ghigo, FD, Gilbank, DG, Giorgini, JD, Gustafsson, A, Hainaut, O, Harris, WM, Jao, JS, Johnson, LS, Kareta, T, Kim, MJ, Koschny, D, Kramer, EA, Landis, RR, Laurin, DG, Larsen, JA, Lee, CG, Lejoly, C, Lister, T, McMillan, R, Masiero, JR, Mathias, D, Mommert, M, Moon, HK, Moskovitz, NA, Naidu, SP, Nallapu, RT, Niazi, HK, Noonan, JW, Polishook, D, Ryan, EV, Schatz, L, Scotti, JV, Sharkey, B, Shustov, BM, Sickafoose, AA, Silva, MA, Slade, MA, Slick, LR, Snedeker, LG, Springmann, A, Tholen, D, Trilling, DE, Vodniza, AQ, Wainscoat, R, Weryk, R & Yoshikawa, M 2019, 'Near-Earth asteroid 2012 TC4 observing campaign: Results from a global planetary defense exercise', Icarus, vol. 326, pp. 133-150. https://doi.org/10.1016/j.icarus.2019.02.018
Reddy V, Kelley MS, Farnocchia D, Ryan WH, Thomas CA, Benner LAM et al. Near-Earth asteroid 2012 TC4 observing campaign: Results from a global planetary defense exercise. Icarus. 2019 Jul 1;326:133-150. https://doi.org/10.1016/j.icarus.2019.02.018
Reddy, Vishnu ; Kelley, Michael S. ; Farnocchia, Davide ; Ryan, William H. ; Thomas, Cristina A. ; Benner, Lance A.M. ; Dotson, Jessie ; Micheli, Marco ; Brucker, Melissa J. ; Bus, Schelte J. ; Brozovic, Marina ; Wheeler, Lorien ; Abbasi, Viqar ; Bauer, James M. ; Bonsall, Amber ; Brown, Zarah L. ; Busch, Michael W. ; Chodas, Paul ; Choi, Young Jun ; Erasmus, Nicolas ; Fast, Kelly E. ; Faucher, John P. ; Fernandes, Rachel B. ; Ghigo, Frank D. ; Gilbank, David G. ; Giorgini, Jon D. ; Gustafsson, Annika ; Hainaut, Olivier ; Harris, Walter M. ; Jao, Joseph S. ; Johnson, Lindley S. ; Kareta, Theodore ; Kim, Myung Jin ; Koschny, Detlef ; Kramer, Emily A. ; Landis, Rob R. ; Laurin, Denis G. ; Larsen, Jeffrey A. ; Lee, Clement G. ; Lejoly, Cassandra ; Lister, Tim ; McMillan, Robert ; Masiero, Joseph R. ; Mathias, Donovan ; Mommert, Michael ; Moon, Hong Kyu ; Moskovitz, Nicholas A. ; Naidu, Shantanu P. ; Nallapu, Ravi Teja ; Niazi, Haris Khan ; Noonan, John W. ; Polishook, David ; Ryan, Eileen V. ; Schatz, Lauren ; Scotti, James V. ; Sharkey, Benjamin ; Shustov, Boris M. ; Sickafoose, Amanda A. ; Silva, Marc A. ; Slade, Martin A. ; Slick, Lindsay R. ; Snedeker, Lawrence G. ; Springmann, Alessandra ; Tholen, David ; Trilling, David E ; Vodniza, Alberto Q. ; Wainscoat, Richard ; Weryk, Robert ; Yoshikawa, Makoto. / Near-Earth asteroid 2012 TC4 observing campaign : Results from a global planetary defense exercise. In: Icarus. 2019 ; Vol. 326. pp. 133-150.
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title = "Near-Earth asteroid 2012 TC4 observing campaign: Results from a global planetary defense exercise",
abstract = "Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characterize smaller objects. In an effort to test our preparedness to respond to a potential NEO impact threat, we conducted a community-led global planetary defense exercise with support from the NASA Planetary Defense Coordination Office. The target of our exercise was 2012 TC4, the ~10 m diameter asteroid that made a close pass by the Earth on 2017 October 12 at a distance of about 50,000 km. The goal of the TC4 observing campaign was to recover, track, and characterize 2012 TC4 as a hypothetical impactor in order to exercise the global planetary defense system involving observations, modeling, prediction, and communication. We made three attempts with the Very Large Telescope (VLT) on 2017 July 27, 31 and on 2017 August 5 and recovered 2012 TC4 within its ephemeris uncertainty at 2.2 arcmin from the nominal prediction. At visual magnitude V = 27, the recovery of 2012 TC4 is the faintest NEA detection thus far. If an impact during the 2017 close approach had been possible based on the 2012 astrometric data, these recovery observations would have been sufficient to confirm or rule out the impact. The first automatic detection by a survey (Pan-STARRS1) was on September 25, which is the earliest that 2012 TC4 would have been discovered in survey mode, if it had not been discovered in 2012. We characterized 2012 TC4 using photometry, spectroscopy and radar techniques. Based on photometric observations, we determined a rotation period of 12.2 min with an amplitude of 0.9 magnitudes. An additional lower amplitude period was detected, indicating that 2012 TC4 was in a state of non-principal axis rotation. The combined visible and near-infrared spectrum puts it in the taxonomic X-class. Radar images at 1.875 m resolution placed only a few range pixels on the asteroid, reveal an angular, asymmetric, and elongated shape, and establish that 2012 TC4 is less than 20 m on its long axis. We estimate a circular polarization ratio of 0.57 + -0.08 that is relatively high among NEAs observed to date by radar. We also performed a probabilistic impact risk assessment exercise for hypothetical impactors based on the 2012 TC4 observing campaign. This exercise was performed as part of ongoing efforts to advance effective impact risk models and assessment processes for planetary defense. The 2012 TC4 close approach provided a valuable opportunity to test the application of these methods using realistically evolving observational data to define the modeling inputs. To this end, risk assessments were calculated at several epochs before and during the close approach, incorporating new information about 2012 TC4 as it became available. Two size ranges were assessed—one smaller size range (H = 26.7) similar to the actual 2012 TC4, and one larger size range (H = 21.9) to produce a greater-damage scenario for risk assessment. Across the epochs, we found that only irons caused significant damage for smaller size. For the larger size case, however, hydrous stones caused the greatest damage, anhydrous stones caused the least damage, and irons caused moderate damage. We note that the extent of damage depends on composition in different size regimes and, after astrometry, size is the most important physical property to determine for an incoming object.",
author = "Vishnu Reddy and Kelley, {Michael S.} and Davide Farnocchia and Ryan, {William H.} and Thomas, {Cristina A.} and Benner, {Lance A.M.} and Jessie Dotson and Marco Micheli and Brucker, {Melissa J.} and Bus, {Schelte J.} and Marina Brozovic and Lorien Wheeler and Viqar Abbasi and Bauer, {James M.} and Amber Bonsall and Brown, {Zarah L.} and Busch, {Michael W.} and Paul Chodas and Choi, {Young Jun} and Nicolas Erasmus and Fast, {Kelly E.} and Faucher, {John P.} and Fernandes, {Rachel B.} and Ghigo, {Frank D.} and Gilbank, {David G.} and Giorgini, {Jon D.} and Annika Gustafsson and Olivier Hainaut and Harris, {Walter M.} and Jao, {Joseph S.} and Johnson, {Lindley S.} and Theodore Kareta and Kim, {Myung Jin} and Detlef Koschny and Kramer, {Emily A.} and Landis, {Rob R.} and Laurin, {Denis G.} and Larsen, {Jeffrey A.} and Lee, {Clement G.} and Cassandra Lejoly and Tim Lister and Robert McMillan and Masiero, {Joseph R.} and Donovan Mathias and Michael Mommert and Moon, {Hong Kyu} and Moskovitz, {Nicholas A.} and Naidu, {Shantanu P.} and Nallapu, {Ravi Teja} and Niazi, {Haris Khan} and Noonan, {John W.} and David Polishook and Ryan, {Eileen V.} and Lauren Schatz and Scotti, {James V.} and Benjamin Sharkey and Shustov, {Boris M.} and Sickafoose, {Amanda A.} and Silva, {Marc A.} and Slade, {Martin A.} and Slick, {Lindsay R.} and Snedeker, {Lawrence G.} and Alessandra Springmann and David Tholen and Trilling, {David E} and Vodniza, {Alberto Q.} and Richard Wainscoat and Robert Weryk and Makoto Yoshikawa",
year = "2019",
month = "7",
day = "1",
doi = "10.1016/j.icarus.2019.02.018",
language = "English (US)",
volume = "326",
pages = "133--150",
journal = "Icarus",
issn = "0019-1035",
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TY - JOUR

T1 - Near-Earth asteroid 2012 TC4 observing campaign

T2 - Results from a global planetary defense exercise

AU - Reddy, Vishnu

AU - Kelley, Michael S.

AU - Farnocchia, Davide

AU - Ryan, William H.

AU - Thomas, Cristina A.

AU - Benner, Lance A.M.

AU - Dotson, Jessie

AU - Micheli, Marco

AU - Brucker, Melissa J.

AU - Bus, Schelte J.

AU - Brozovic, Marina

AU - Wheeler, Lorien

AU - Abbasi, Viqar

AU - Bauer, James M.

AU - Bonsall, Amber

AU - Brown, Zarah L.

AU - Busch, Michael W.

AU - Chodas, Paul

AU - Choi, Young Jun

AU - Erasmus, Nicolas

AU - Fast, Kelly E.

AU - Faucher, John P.

AU - Fernandes, Rachel B.

AU - Ghigo, Frank D.

AU - Gilbank, David G.

AU - Giorgini, Jon D.

AU - Gustafsson, Annika

AU - Hainaut, Olivier

AU - Harris, Walter M.

AU - Jao, Joseph S.

AU - Johnson, Lindley S.

AU - Kareta, Theodore

AU - Kim, Myung Jin

AU - Koschny, Detlef

AU - Kramer, Emily A.

AU - Landis, Rob R.

AU - Laurin, Denis G.

AU - Larsen, Jeffrey A.

AU - Lee, Clement G.

AU - Lejoly, Cassandra

AU - Lister, Tim

AU - McMillan, Robert

AU - Masiero, Joseph R.

AU - Mathias, Donovan

AU - Mommert, Michael

AU - Moon, Hong Kyu

AU - Moskovitz, Nicholas A.

AU - Naidu, Shantanu P.

AU - Nallapu, Ravi Teja

AU - Niazi, Haris Khan

AU - Noonan, John W.

AU - Polishook, David

AU - Ryan, Eileen V.

AU - Schatz, Lauren

AU - Scotti, James V.

AU - Sharkey, Benjamin

AU - Shustov, Boris M.

AU - Sickafoose, Amanda A.

AU - Silva, Marc A.

AU - Slade, Martin A.

AU - Slick, Lindsay R.

AU - Snedeker, Lawrence G.

AU - Springmann, Alessandra

AU - Tholen, David

AU - Trilling, David E

AU - Vodniza, Alberto Q.

AU - Wainscoat, Richard

AU - Weryk, Robert

AU - Yoshikawa, Makoto

PY - 2019/7/1

Y1 - 2019/7/1

N2 - Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characterize smaller objects. In an effort to test our preparedness to respond to a potential NEO impact threat, we conducted a community-led global planetary defense exercise with support from the NASA Planetary Defense Coordination Office. The target of our exercise was 2012 TC4, the ~10 m diameter asteroid that made a close pass by the Earth on 2017 October 12 at a distance of about 50,000 km. The goal of the TC4 observing campaign was to recover, track, and characterize 2012 TC4 as a hypothetical impactor in order to exercise the global planetary defense system involving observations, modeling, prediction, and communication. We made three attempts with the Very Large Telescope (VLT) on 2017 July 27, 31 and on 2017 August 5 and recovered 2012 TC4 within its ephemeris uncertainty at 2.2 arcmin from the nominal prediction. At visual magnitude V = 27, the recovery of 2012 TC4 is the faintest NEA detection thus far. If an impact during the 2017 close approach had been possible based on the 2012 astrometric data, these recovery observations would have been sufficient to confirm or rule out the impact. The first automatic detection by a survey (Pan-STARRS1) was on September 25, which is the earliest that 2012 TC4 would have been discovered in survey mode, if it had not been discovered in 2012. We characterized 2012 TC4 using photometry, spectroscopy and radar techniques. Based on photometric observations, we determined a rotation period of 12.2 min with an amplitude of 0.9 magnitudes. An additional lower amplitude period was detected, indicating that 2012 TC4 was in a state of non-principal axis rotation. The combined visible and near-infrared spectrum puts it in the taxonomic X-class. Radar images at 1.875 m resolution placed only a few range pixels on the asteroid, reveal an angular, asymmetric, and elongated shape, and establish that 2012 TC4 is less than 20 m on its long axis. We estimate a circular polarization ratio of 0.57 + -0.08 that is relatively high among NEAs observed to date by radar. We also performed a probabilistic impact risk assessment exercise for hypothetical impactors based on the 2012 TC4 observing campaign. This exercise was performed as part of ongoing efforts to advance effective impact risk models and assessment processes for planetary defense. The 2012 TC4 close approach provided a valuable opportunity to test the application of these methods using realistically evolving observational data to define the modeling inputs. To this end, risk assessments were calculated at several epochs before and during the close approach, incorporating new information about 2012 TC4 as it became available. Two size ranges were assessed—one smaller size range (H = 26.7) similar to the actual 2012 TC4, and one larger size range (H = 21.9) to produce a greater-damage scenario for risk assessment. Across the epochs, we found that only irons caused significant damage for smaller size. For the larger size case, however, hydrous stones caused the greatest damage, anhydrous stones caused the least damage, and irons caused moderate damage. We note that the extent of damage depends on composition in different size regimes and, after astrometry, size is the most important physical property to determine for an incoming object.

AB - Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characterize smaller objects. In an effort to test our preparedness to respond to a potential NEO impact threat, we conducted a community-led global planetary defense exercise with support from the NASA Planetary Defense Coordination Office. The target of our exercise was 2012 TC4, the ~10 m diameter asteroid that made a close pass by the Earth on 2017 October 12 at a distance of about 50,000 km. The goal of the TC4 observing campaign was to recover, track, and characterize 2012 TC4 as a hypothetical impactor in order to exercise the global planetary defense system involving observations, modeling, prediction, and communication. We made three attempts with the Very Large Telescope (VLT) on 2017 July 27, 31 and on 2017 August 5 and recovered 2012 TC4 within its ephemeris uncertainty at 2.2 arcmin from the nominal prediction. At visual magnitude V = 27, the recovery of 2012 TC4 is the faintest NEA detection thus far. If an impact during the 2017 close approach had been possible based on the 2012 astrometric data, these recovery observations would have been sufficient to confirm or rule out the impact. The first automatic detection by a survey (Pan-STARRS1) was on September 25, which is the earliest that 2012 TC4 would have been discovered in survey mode, if it had not been discovered in 2012. We characterized 2012 TC4 using photometry, spectroscopy and radar techniques. Based on photometric observations, we determined a rotation period of 12.2 min with an amplitude of 0.9 magnitudes. An additional lower amplitude period was detected, indicating that 2012 TC4 was in a state of non-principal axis rotation. The combined visible and near-infrared spectrum puts it in the taxonomic X-class. Radar images at 1.875 m resolution placed only a few range pixels on the asteroid, reveal an angular, asymmetric, and elongated shape, and establish that 2012 TC4 is less than 20 m on its long axis. We estimate a circular polarization ratio of 0.57 + -0.08 that is relatively high among NEAs observed to date by radar. We also performed a probabilistic impact risk assessment exercise for hypothetical impactors based on the 2012 TC4 observing campaign. This exercise was performed as part of ongoing efforts to advance effective impact risk models and assessment processes for planetary defense. The 2012 TC4 close approach provided a valuable opportunity to test the application of these methods using realistically evolving observational data to define the modeling inputs. To this end, risk assessments were calculated at several epochs before and during the close approach, incorporating new information about 2012 TC4 as it became available. Two size ranges were assessed—one smaller size range (H = 26.7) similar to the actual 2012 TC4, and one larger size range (H = 21.9) to produce a greater-damage scenario for risk assessment. Across the epochs, we found that only irons caused significant damage for smaller size. For the larger size case, however, hydrous stones caused the greatest damage, anhydrous stones caused the least damage, and irons caused moderate damage. We note that the extent of damage depends on composition in different size regimes and, after astrometry, size is the most important physical property to determine for an incoming object.

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