Direct observations of asteroid interior and regolith structure: Science measurement requirements

Hérique, Alain; Agnus, Benoit; Asphaug, Erik; Barucci, A.; Beck, Pierre; Bellerose, Julie; Biele, Jens; Bonal, L.; Bousquet, Pierre; Bruzzone, Lorenzo; Buck, Christopher; Carnelli, Ian; Cheng, A. F.; Ciarletti, Valérie; Delbò, M.; Du, Jun; Du, Xufeng; Eyraud, Christelle; Fa, Wenzhe; Fernandez, Jesus Gil; Gassot, Oriane; Granados-Alfaro, R.; Green, Simon; Grieger, B.; Grundmann, Jan Thimo; Grygorczuk, J.; Hahnel, Ronny; Heggy, E.; Ho, Tra‐Mi; Karatekin, Özgür; Kasaba, Yasumasa; Kobayashi, Tatsuharu; Kofman, W.; Krause, Christian; Kumamoto, A.; Küppers, M.; Laabs, Martin; Lange, Caroline; Lasue, J.; Levasseur-Regourd, A. C.; Mallet, Alfred; Michel, Patrick; Mottola, S.; Murdoch, Naomi; Mütze, Marco; Oberst, J.; Orosei, R.; Plettemeier, Dirk; Rochat, S.; Rodriguez-Suquet, R.; Rogez, Yves; Schaffer, Petr; Snodgrass, C.; Souyris, J.-C.; Tokarz, M.; Ulamec, Stephan; Wahlund, J. E.; Zine, Sonia

doi:10.1016/j.asr.2017.10.020

Cited by 59 publications

(38 citation statements)

References 94 publications

(105 reference statements)

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“…The pore size ζ in the interior is related to grain size, often a major unknown (Asphaug et al, ). Hérique et al () indicate that regolith on asteroidal surfaces has a size range from microns to a meter, and the internal aggregate may be coarser than that. We choose a value of ζ = 1 cm and note that t D is proportional to ζ and R is proportional to

\sqrt{ζ}

.…”

Section: Model Of Ice Retreatmentioning

confidence: 99%

Ice Loss From the Interior of Small Airless Bodies According to an Idealized Model

Schörghofer

Hsieh

2018

JGR Planets

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Ice in main belt asteroids and near‐Earth objects is of scientific and resource exploration interest, but small airless bodies gradually lose their ice to space by outward diffusion. Here we quantitatively estimate the time it takes a porous airless body to lose all of its interior ice, based on an analytic solution for the interior temperature field of bodies in stable orbits. Without latent heat, the average surface temperature, which is lower than the classic effective temperature, is representative of the body interior and hence an appropriate temperature to evaluate desiccation timescales. In a spherically averaged model, an explicit analytic solution is obtained for the depth to ice as a function of time and the time to complete desiccation. Half of the ice volume is lost after 11% of this time. A bilobate structure emerges from the strong latitude dependence of desiccation rates. Cold polar regions can harbor subsurface ice, even when the body center does not. Latent heat retards ice loss, and we obtain a succinct expression for the temperature difference between the surface and the ice. In the outer main belt, nearly all bodies 10 km in size or larger should have been able to retain ice in their interiors over the age of the solar system. Each of the following factors favors the presence of ice inside near‐Earth objects: a semimajor axis in the outer belt or beyond, a mantle of very low thermal inertia, a young age, or a small and stable axis tilt.

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\sqrt{ζ}

.…”

Section: Model Of Ice Retreatmentioning

confidence: 99%

Ice Loss From the Interior of Small Airless Bodies According to an Idealized Model

Schörghofer

Hsieh

2018

JGR Planets

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“…These differences in spin properties indicate that the internal structure of large and small objects could be different. While larger objects are usually considered to be rubble-piles, smaller ones could either be monolithic or possess sufficient internal strength to prevent them from breaking apart due to the centrifugal acceleration imparted by rapid rotation (Hérique et al 2018;Rozitis et al 2014;Polishook et al 2017b).…”

Section: Introductionmentioning

confidence: 99%

Visible Spectroscopy from the Mission Accessible Near-Earth Object Survey (MANOS): Taxonomic Dependence on Asteroid Size

Devogèle

Moskovitz

Thirouin

et al. 2019

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The Mission Accessible Near-Earth Object Survey (MANOS) aims to observe and characterize small (mean absolute magnitude H ∼ 25 mag) Near-Earth Objects (NEOs) that are accessible by spacecraft (mean ∆v ∼ 5.7 km/s) and that make close approaches with the Earth (mean Minimum Orbital Intersection Distance MOID ∼ 0.03 AU). We present here the first results of the MANOS visible spectroscopic survey. The spectra were obtained from August 2013 to March 2018 at Lowell Observatory's Discovery Channel 4.3 meter telescope, and both Gemini North and South facilities. In total, 210 NEOs have been observed and taxonomically classified. Our taxonomic distribution shows significant variations with respect to surveys of larger objects. We suspect these to be due to a dependence of Main Belt source regions on object size. Compared to previous surveys of larger objects (Binzel et al. 2019Perna et al. 2018), we report a lower fraction of S+Q-complex asteroids of 43.8 ± 4.6%. We associate this decrease with a lack of Phocaea family members at very small size. We also report higher fractions of X-complex and A-type asteroids of 23.8 ± 3.3% and 3.8 ± 1.3% respectively due to an increase of Hungaria family objects at small size. We find a strong correlation between the Q/S ratio and perihelion distance. We suggest this correlation is due to planetary close encounters with Venus playing a major role in turning asteroids from S to Q-type. This hypothesis is supported by a similar correlation between the Q/S ratio and Venus MOID.

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“…Laboratory measurements show relatively higher loss tangent values for phyllosilicates than for anhydrate silicates in general, and even higher loss tangent values for various phases of carbons (cf. Herique et al 2016Herique et al , 2018, although those measurements were all made at dm to m wavelengths, which are much longer than those of our observations. Therefore, the hot surface of Ceres at sub-mm and mm wavelengths could be due to the unique composition of Ceres's top layer, where regolith material is opaque to mm wavelength thermal emission, but more transparent to longer wavelength due to material with grain sizes of tens of µm or smaller that makes up the top surface of Ceres.…”

Section: Implications Of High Electrical Absorptionmentioning

confidence: 58%

Disk-integrated Thermal Properties of Ceres Measured at Millimeter Wavelengths

Moullet²,

Titus

et al. 2020

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We observed Ceres at three epochs in 2015 November and 2017 September and October with ALMA 12-meter array and in 2017 October with the ALMA Compact Array (ACA), all at ~265 GHz continuum (wavelengths of ~1.1 mm) to map the temperatures of Ceres over a full rotation at each epoch. We also used 2017 October ACA observations to search for HCN. The disk-averaged brightness temperature of Ceres is measured to be between 170 K and 180 K during our 2017 observations. The rotational lightcurve of Ceres shows a double peaked shape with an amplitude of about 4%. Our HCN search returns a negative result with an upper limit production rate of ~2´10 24 molecules s -1 , assuming globally uniform production and a Haser model. A thermophysical model suggests that Ceres's top layer has higher dielectric absorption than lunarlike materials at a wavelength of 1 mm. However, previous observations showed that the dielectric absorption of Ceres decreases towards longer wavelengths. Such distinct dielectric properties might be related to the hydrated phyllosilicate composition of Ceres and possibly abundant µm-sized grains on its surface. The thermal inertia of Ceres is constrained by our modeling as likely being between 40 and 160 tiu, much higher than previous measurements at infrared wavelengths. Modeling also suggests that Ceres's lightcurve is likely dominated by spatial variations in its physical or compositional properties that cause changes in Ceres's observed thermal properties and dielectric absorption as it rotates. Accepted by Astronomical Journal

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Direct observations of asteroid interior and regolith structure: Science measurement requirements

Cited by 59 publications

References 94 publications

Ice Loss From the Interior of Small Airless Bodies According to an Idealized Model

Ice Loss From the Interior of Small Airless Bodies According to an Idealized Model

Visible Spectroscopy from the Mission Accessible Near-Earth Object Survey (MANOS): Taxonomic Dependence on Asteroid Size

Disk-integrated Thermal Properties of Ceres Measured at Millimeter Wavelengths

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