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
また、ベンヌの密度が1.19というのも衝撃的だった。イトカワの1.9に比べてもスカスカ度が半端ない。このあたりの差が、小惑星のでき方、さらにいえば地球近傍小惑星のでき方にも関わってくるだろう。 #LPSC2019
2019-03-19 23:11:07
Junya Terazono 寺薗淳也
@terakinizers
How Good are our Effort ? (Stereophotoclinometry) (Asad): Stereophotometry and laser altimetry is used to determine shape of #Bennu . "SPC: Photo capturing -> Some Magic :) -> topography" #OSIRISREx #LPSC2019
2019-03-19 23:19:26
Junya Terazono 寺薗淳也
@terakinizers
今回のオシリス・レックスの発表、 #はやぶさ2 チームの面々が次々に質問している。おそらく午後にはこの逆のシーンがみられるのだろう。 #LPSC2019
2019-03-19 23:27:19
Junya Terazono 寺薗淳也
@terakinizers
The Gravity and Global Geophysical Environment of #Bennu (Scheeres): Bennu's gravitational parameter determined through 5 flybys. Poles 8 μG & 3μG at equator. #OSIRISREx #LPSC2019
2019-03-19 23:33:30
Junya Terazono 寺薗淳也
@terakinizers
Possible material flows from pole to equator seen in gravitational anaylsis. This occurs where the rotational Roche lobe intersects the surface. #OSIRISREx #LPSC2019
2019-03-19 23:35:57
Junya Terazono 寺薗淳也
@terakinizers
#Bennu is spinning up, and doubles its rate in 1.5 MY. And migrates with spin rates, materials moves to the equater with increasing spin. The surface has undergone siginificant topographic change in the RECENT past. #OSIRISREx #LPSC2019
2019-03-19 23:39:19
Junya Terazono 寺薗淳也
@terakinizers
" #Bennu 's density is consistent with #Ryugu and with the ground-based estimates." Bulk density is 1.19 an GM = 4.892 m3/s2 #OSIRISREx #LPSC2019
2019-03-19 23:44:02
Junya Terazono 寺薗淳也
@terakinizers
Brightness, Color & Morphology of #Bennu (Rizk): Albedo is 4.4% in averate and consistend with one of chondrites. #OSIRISREx #LPSC2019
2019-03-19 23:46:42
Junya Terazono 寺薗淳也
@terakinizers
#Bennu is a true rubble-pile object, diverse, cratered, blackened with wide variety of boulders. #OSIRISREx #LPSC2019
2019-03-19 23:48:30
Junya Terazono 寺薗淳也
@terakinizers
#Bennu is a site of rich planetary geology. From large to small scale, the images shows geological process on Bennu, particularly by Boulders (from m scale to cm scale). #OSIRISREx #LPSC2019
2019-03-19 23:52:45
Junya Terazono 寺薗淳也
@terakinizers
#Bennu 's global geology (Walsh): overview is geology of #Bennu is explained with Craters, Boulders and Regolith. 120m crater candidate seen near equator. Several 10 meters of craters seen in various places in surface. #OSIRISREx #LPSC2019
2019-03-20 00:02:25
Junya Terazono 寺薗淳也
@terakinizers
#Bennu 's surface age is estimated as ~100M to ~1G yr. Also clear falloff in craters around ~50m. Equatrial Ridge is an old feature, multiple D>100m covers on it. #OSIRISREx #LPSC2019
2019-03-20 00:03:46
Junya Terazono 寺薗淳也
@terakinizers
Boulders: two quite large boulders, approx 50m, on #Bennu . Some evidence of movement of boulders seen in surface. Fracture boulders found in some places. #OSIRISREx #LPSC2019
2019-03-20 00:07:08
Junya Terazono 寺薗淳也
@terakinizers
Fractured boulders sees characteristics of impact breccia. #Bennu #OSIRISREx #LPSC2019
2019-03-20 00:08:04
Junya Terazono 寺薗淳也
@terakinizers
160m crater candidate has large-scale movement of materials. There is a flow into this. #Bennu #OSIRISREx #LPSC2019
2019-03-20 00:09:22
Junya Terazono 寺薗淳也
@terakinizers
Regolith of #Bennu . Small craters show absense of large boulders, and appear to be promising location for collection of small samples. #OSIRISREx #LPSC2019
2019-03-20 00:11:23
Junya Terazono 寺薗淳也
@terakinizers
Crater Erasure on Small Bodies (Ballouz): Two mechanism ... seismic shaking from impacts, and torques induced from solar heating. Crater size disruption in 50m may show evidence of crater erasure mechanism. #OSIRISREx #Bennu #LPSC2019
2019-03-20 00:18:24
Junya Terazono 寺薗淳也
@terakinizers
Impacts of more than several tens of meters in diameter is sufficient to move regolith on #Bennu surface by vibration. But impactors with 10m in diameter is too large for Bennu survival. Low-frequency (<1Hz)seismic wave will solve this paradox. #Bennu #OSIRISREx #LPSC2019
2019-03-20 00:23:49
Junya Terazono 寺薗淳也
@terakinizers
Another factor of mobilization is spin evolution of #Bennu . Also, ballistic redistribution of material maybe the interesting point of material moving. #OSIRISREx #LPSC2019
2019-03-20 00:26:44
Junya Terazono 寺薗淳也
@terakinizers
Geology of #Bennu 's Biggest Boulders (Jawin): 3100 boulders ranging from 1 to 58 m in diameter in Bennu. 14 boulders are >30m in diam. Rocks with >20m diam inherited from Bennu parent body. #OSIRISREx #LPSC2019
2019-03-20 00:30:50
Junya Terazono 寺薗淳也
@terakinizers
The largest two boulders, 1 = 95m, 2 = 58m in diameter. B1 has 4.5% albedo, fine-grained surface texture, two surface texture: smooth hummocky, overhanging. #OSIRISREx #LPSC2019
2019-03-20 00:32:51
Junya Terazono 寺薗淳也
@terakinizers
Boulder 2: Albedo of 3.5%, hummocky texture, clasts, rounded, flat aspect ratio. Deposits of fine grained material on the top of boulder. This boulder is hallfly buried. No overhang seen in boulder 2. #Bennu #OSIRISREx #LPSC2019
2019-03-20 00:36:15
Junya Terazono 寺薗淳也
@terakinizers
Spectral absorption around 550nm implies existence of magnetite. This may be alteration product from CI/CM chondrite parent body or space weathering . #Bennu #OSIRISREx #LPSC2019
2019-03-20 00:38:03
Junya Terazono 寺薗淳也
@terakinizers
@elakdawalla Switching duration of slides are also too fast to grasp all content displayed. I have great difficulty in writing tweets seeing slides with hearing explanation. #LPSC2019
2019-03-20 00:39:00