月惑星科学会議（LPSC）：OSIRIS-REx と小惑星ベンヌ（ベヌー）
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SubaruTakeshima
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Junya Terazono 寺薗淳也
@terakinizers
おはようございます。ヒューストン、というかザ・ウッドランズは少し肌寒い朝。雲が多い天気だが雨の心配はなく快適な気候だ。ヒューストン特有の蒸し暑さもない。
2019-03-19 22:10:41
Junya Terazono 寺薗淳也
@terakinizers
今日はこれから、本学会の最大のみどころ(ということにしておく)、オシリス・レックスと #はやぶさ2 の競演だ。同じ会場(部屋)で午前中はオシリス・レックス、午後がはや2。まさに50回にふさわしい宿命の対決(？)だ。#LPSC2019
2019-03-19 22:13:31
Junya Terazono 寺薗淳也
@terakinizers
Today, we will have #OSIRISREx session in the morning and #hayabusa2 session in the afternoon. Do not confuse Bennu & Ryugu :) #LPSC2019 pic.twitter.com/FiCYB2hE1W
2019-03-19 22:28:39
拡大
拡大
Junya Terazono 寺薗淳也
@terakinizers
#OSIRISREx arrives at Bennu (Lauretta): "It's a 15-years personal journey to make shape of the mission". Definitely!
2019-03-19 22:32:19
Junya Terazono 寺薗淳也
@terakinizers
"The most exciting part of the mission is collaboration with JAXA members" ... referring to #Hayabusa2 .
2019-03-19 22:32:57
Junya Terazono 寺薗淳也
@terakinizers
Preliminary survey until Apr 2019, Detailed survey from Apr 2019 to Sep, Recon phase from Sep 2019, Rehearsal from Beginning of 2020. Sample collection July 2020. #OSIRISREx #LPSC2019
2019-03-19 22:34:12
Junya Terazono 寺薗淳也
@terakinizers
#OSIRISREx awarded Guiness World Record for the orbiter with the smallest asteorid. Awesome! #LPSC2019
2019-03-19 22:34:58
Junya Terazono 寺薗淳也
@terakinizers
#Bennu rotation rate is increasing. Accelerated since 1999, and continue to present. Most likely due to the YORP effect. Rotation period is apporox 4.3 hrs. #OSIRISREx #LPSC2019
2019-03-19 22:36:04
Junya Terazono 寺薗淳也
@terakinizers
Abundant Hydrated minerals and magnetite found in the surface of #Bennu according to spectral data analysis. #OSIRISREx #LPSC2019
2019-03-19 22:37:42
Junya Terazono 寺薗淳也
@terakinizers
#Bennu is spinning top shape as expected. Density is 1.19, implying rubble-pile style object. Bennu also have large variatoin of Albedo, ranging from 0.035 to 0.05. Large boulders( >30m) have near-average albedo 0.044. #OSIRISREx #LPSC2019
2019-03-19 22:39:43
Junya Terazono 寺薗淳也
@terakinizers
#Bennu is covered with rocks, very rugged and rough surface according to images captured by POLYCAM. Preliminary sampling site assessment is ongoing and some candidates identified. #OSIRISREx #LPSC2019
2019-03-19 22:42:36
Junya Terazono 寺薗淳也
@terakinizers
The most suprising fact is that #Bennu is "active" asteroid, trajectory from the asteroid captured by NavCam. "We are seeing new activity on Asteroid"! #OSIRISREx #LPSC2019
2019-03-19 22:44:02
Junya Terazono 寺薗淳也
@terakinizers
It revealed #Bennu is a very characteristic and active. It will be big issue for future asteroid mission to search such an "active" asteroid and its origin. #OSIRISREx #LPSC2019
2019-03-19 22:45:30
Emily Lakdawalla
@elakdawalla
OK, definitely the #1 most fascinating thing from Dante Lauretta's opening OSIRIS-REx presentation: 11 times Bennu has erupted material from its surface, at a few cm/s to a few m/s, some of which ends up in bound orbits around Bennu. How!? Why!? #LPSC2019
2019-03-19 22:45:36
Junya Terazono 寺薗淳也
@terakinizers
Investigating the Shape of Bennu (Barnouin): Earth-based radar model had good resembles with observation result. Density is, again, 1.19 (Itokawa is 1.9, so more porous). #OSIRISREx #LPSC2019
2019-03-19 22:50:33
Junya Terazono 寺薗淳也
@terakinizers
#Bennu has N-S asymmetry according to spherical harmonic assessment. Unusually large sectoral (longitudal) terms found. #OSIRISREx #LPSC2019
2019-03-19 22:52:00
Junya Terazono 寺薗淳也
@terakinizers
At least two ridges extend from north to south poles (90 deg). Elevation hypsometry is very similar to Itokawa. #OSIRISREx #Bennu #LPSC2019
2019-03-19 22:53:14
Junya Terazono 寺薗淳也
@terakinizers
Boulders of #Bennu: several >40m in diameter, large boulders >3m dominate surface roughness. Impact craters present. Depth-to-diameter ratio exceeds 0.1, like Eros. #OSIRISREx #LPSC2019
2019-03-19 22:56:08
Junya Terazono 寺薗淳也
@terakinizers
There are many surface linearments, grooves, troughs and they are more well-shaped than that on Itokawa. #Bennu #OSIRISREx #LPSC2019
2019-03-19 22:57:23
Junya Terazono 寺薗淳也
@terakinizers
Maybe #Bennu is a result of disruption and reaccumulation, like Itokawa. #Bennu is recently stiffend and created grooves and scarps. And recent mass wasting. #OSIRISREx #LPSC2019
2019-03-19 22:59:04
Junya Terazono 寺薗淳也
@terakinizers
The global surface roughness (Susorney): Topography is low in equatorial region and high in polar region. Surface roughness comparison with Eros and Itokawa. #OSIRISREx #Bennu #LPSC2019
2019-03-19 23:02:05
Junya Terazono 寺薗淳也
@terakinizers
The surface roughness at 5m scale is dominated by boulders, bright spots seen frequently seen in #Bennu surface. Linearment provide a smaller contribution. Large-scaled structure is sensitive to 20m scale. #LPSC2019 #OSIRISREx
2019-03-19 23:05:12
Junya Terazono 寺薗淳也
@terakinizers
Surface roughness of #Bennu does not have large spatial variagions as compared in Eros and Itokawa. Maybe this difference stems from their difference of shape. #OSIRISREx #LPSC2019
2019-03-19 23:07:24
Junya Terazono 寺薗淳也
@terakinizers
ベンヌに「何らかの活動の証拠がある」という発表は衝撃的だった。普通そんなことはまず考えていないはずの小惑星にそういう証拠がみつかったということは、今後他の小惑星(とりわけリュウグウ)も詳細に調べてみないといけないということだろう。 #LPSC2019
2019-03-19 23:10:07