Near-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration

Takir, D.; Kareta, Theodore; Emery, Joshua P.; Hanuš, Josef; Reddy, V.; Howell, E. S.; Rivkin, Andrew S.; Arai, Tomoko

doi:10.1038/s41467-020-15637-7

Cited by 30 publications

(26 citation statements)

References 33 publications

(44 reference statements)

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“…It is unlikely that activity at Phaethon is driven by the sublimation of near‐surface ices; rather, the leading mechanisms for particle production are thermal stress fracturing and radiation pressure sweeping (Jewitt & Li, 2010). The nondetection of hydrated minerals on the surface of Phaethon also casts doubt on phyllosilicate dehydration as an activity mechanism (Takir et al, 2020). A second small‐perihelion object has been found to experience activity.…”

Section: Bennu's Activity and Its Place Within The Population Of Actimentioning

confidence: 99%

Introduction to the Special Issue: Exploration of the Activity of Asteroid (101955) Bennu

et al. 2020

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Near‐Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss. The activity manifests itself in the form of ejection events emitting up to hundreds of millimeter‐ to centimeter‐scale particles. The Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer spacecraft monitored particle activity for a 10‐month period that included Bennu's perihelion and aphelion. Novel and classical methods were utilized to detect the particles and characterize their orbital and physical properties. Roughly 30% of the observed particle mass escaped to heliocentric orbit. A majority of particles fell back onto the surface of Bennu after ejection, with the longest‐lived particle surviving for 6 days on a temporary orbit. Particle ejection events appear to preferentially take place in the afternoon and evening and from low latitudes, although they can occur at any time or latitude. The reaccumulation of material is biased toward low latitudes resulting in the possible in‐fill of craters and growth of Bennu's equatorial bulge. Of the potential mechanisms behind this activity that were investigated in focused studies, meteoroid impacts, thermal fracturing, and ricochet—but not water ice sublimation—were found to be consistent with observations. While phyllosilicate dehydration was not investigated with a focused study, it remains a possible mechanism. These mechanisms are not unique to Bennu, suggesting that many near‐Earth asteroids may exhibit activity that has gone undetected thus far. Spacecraft missions with wide‐field imagers are encouraged to further characterize this phenomenon.

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Section: Bennu's Activity and Its Place Within The Population Of Actimentioning

confidence: 99%

Introduction to the Special Issue: Exploration of the Activity of Asteroid (101955) Bennu

et al. 2020

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“…Moreover, a correlation between brighter and bluer spectra was also observed 31 . The similarity for both Ryugu and Phaethon, that neither exhibits a strong UV nor 2.7-µm OH-band absorption for the entire rotational phases 40 , suggests similar spectral changes due to space weathering on both asteroids. Thus, the majority of Phaethon’s surface could be fresh due to rejuvenation caused by the recent encounter with the Sun, i.e., fresh cometary activity.…”

Section: Resultsmentioning

confidence: 88%

Spectrally blue hydrated parent body of asteroid (162173) Ryugu

et al. 2021

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Ryugu is a carbonaceous rubble-pile asteroid visited by the Hayabusa2 spacecraft. Small rubble pile asteroids record the thermal evolution of their much larger parent bodies. However, recent space weathering and/or solar heating create ambiguities between the uppermost layer observable by remote-sensing and the pristine material from the parent body. Hayabusa2 remote-sensing observations find that on the asteroid (162173) Ryugu both north and south pole regions preserve the material least processed by space weathering, which is spectrally blue carbonaceous chondritic material with a 0–3% deep 0.7-µm band absorption, indicative of Fe-bearing phyllosilicates. Here we report that spectrally blue Ryugu’s parent body experienced intensive aqueous alteration and subsequent thermal metamorphism at 570–670 K (300–400 °C), suggesting that Ryugu’s parent body was heated by radioactive decay of short-lived radionuclides possibly because of its early formation 2–2.5 Ma. The samples being brought to Earth by Hayabusa2 will give us our first insights into this epoch in solar system history.

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“…While water could be bound up in hydrated silicates, experiments by Garenne et al (2014) have shown that these minerals in meteorites begin losing mass below 873 K, well below Phaethon's perihelion temperature. Recent spectral observations by Takir et al (2020) have indicated an absence of hydrated minerals on the surface, further supporting the conclusion that they are not the source of activity.…”

Section: Introductionmentioning

confidence: 73%

Volatility of Sodium in Carbonaceous Chondrites at Temperatures Consistent with Low-Perihelia Asteroids

Masiero,

Davidsson,

Liu

et al. 2021

Preprint

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Solar system bodies with surface and sub-surface volatiles will show observational evidence of activity when they reach a temperature where those volatiles change from solid to gas and are released. This is most frequently seen in comets, where activity is driven by the sublimation of water, carbon dioxide, or carbon monoxide ices. However, some bodies (notably the asteroid (3200) Phaethon) show initiation of activity at very small heliocentric distances, long after they have reached the sublimation temperatures of these ices. We investigate whether the sodium present in the mineral matrix could act as the volatile element responsible for this activity. We conduct theoretical modeling which indicates that sodium has the potential to sublimate in the conditions that Phaethon experiences, depending on the mineral phase it is held in. To test this, we then exposed samples of the carbonaceous chondrite Allende to varying heating events similar to what would be experienced by low perihelion asteroids. We measured the change in sodium present in each sample, and find that the highest temperature samples show a significant loss of sodium from specific mineral phases over a single heating event, comparable to a day on the surface of Phaethon. Under specific thermal histories possible for Phaethon, this outgassing could be sufficient to explain this object's observed activity. This effect would also be expected to be observed for other lowperihelia asteroids as well, and may act as a critical step in the process of disrupting small low-albedo asteroids.

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Near-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration

Cited by 30 publications

References 33 publications

Introduction to the Special Issue: Exploration of the Activity of Asteroid (101955) Bennu

Introduction to the Special Issue: Exploration of the Activity of Asteroid (101955) Bennu

Spectrally blue hydrated parent body of asteroid (162173) Ryugu

Volatility of Sodium in Carbonaceous Chondrites at Temperatures Consistent with Low-Perihelia Asteroids

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