粉体への衝突現象で見られるエジェクタ地形の分類
A. Suzuki1, T. Kadono2, M. Arakawa3, A. M. Nakamura1,K. Wada4, S. Yamamoto5
1CPS/Grad. School Sci., Kobe Univ.，2Inst. Laser Eng., Osaka Univ.,
3Grad. School Env. Studies, Nagoya Univ.，4PERC, Chitech,
5National Inst. Env. Studies

Rayed craters on planets
Kuiper, D=62 kmMoon

๏ The nature, origin, age, and formation processes havelong been the subject of major controversies [e.g.
Hawke et al., 2004]
10/05/25 Mercury
連合大会
NASA/Johns Hopkins Univ. APL/Carnegie Inst. of Washington

火星エジェクタのバリエーションMOUGINIS-MARK: SECOND MARS COLLOQUIUM[Mouginis-Mark, 1979]

8013

seminar namep. 111-136; [2] Schultz, P. H. (1976), Moon Morphology, U.

oon (23 Texaskm/s).
2: Obliquepress, For
628pp;retro[3] Hawke, B.Figure
R. et al. (2004),
Icarus impact craters on Mars illustrating car170,
1-16;
[4]
McEwenA.
S.,
etal.
(2005),
Icarus176,351rcury, the projectile will be
dioid-shaped uprange(left) and composite crater, Dilly
381; [5] Tornabene, L. L., et al. (2006), J. Geophys. Res.
same sizecraterthe [6] Schultz(right).
similarity
with other ballistic ray patterns indi111(E10),
CiteIDon
E10006;
P.H. The(1988),
Lunarand Planet.
Sci. XIX, LPI, Houston,pp.
1039-1040;[7]), however,the projectiles
cates for a curtain-driven vortex origin for the terminal ramWrobel, K. et al. (2006), MAPS, 41, Issue 10, p.1539-1550;
nsequently,
the uprange
ray (2007), Icarus
parts.190,
The295-333;
small crater
Dilly (2 km diameter) exhibits a low[8] Schultz,
P. H., et al.,[9]Figure 4: Conceptual depiction for origin of cardioid ray
Herrick, R.
et al. (2008),
LPSC 38, No.
1391;[10]Anderson,
to impactor
type(comet
thermal inertia (dark) distalarachnidpattern andhigh- center durpatternthat mapsraythe migrationof theaflow-field
J. L. B. and Schultz, P. H. (2006), LPSC 37, abstract
ique impacts.
Retrogradeexcavation.
thermalinertiaJ. Geoproximalingrim
deposits. This suggests a lowno.1726; [11] Schultz P.H. and Gault
D.E. (1984),
rays evenobliquephys.thoughRes. 90, pp.
3701-3732; [12] density
Anderson,surface
J. L. B. etal.
layer.
(2003),
MAPS 39, 303-320.
e), whereas
prograde
astercardioid rays. Oblique imFigure 3: Example of
Figure 1: Farside
d be characterized by thecardioid shaped ray
lunar crater Jackson (71ue to lower impact speeds.
km diameter) exhibitpattern uprange for an
ing distinctive cardioidrials (e.g., aeolian loess),
oblique hypervelocity
uprange ray systemarachnid ray patterns (Fig.
impact (~ 5 km/s) into
similar to Tycho.

ejecta in the laboratory

๏Uprange ray pattern -- interpreted as an evolving
excavation flow field [Schultz et al., 2009]SCHULTZ.'ATMOSPHERICEFFECTSOF EIECTAEMI'I.ACEMENT

11,625Figure 5: Evolution of in-flight ejecta at 160 ms after im-te ray patterns provide newtering flow field and can beovide conditions of impact.

4) Proc. Lunar Sci. Conf-, Sth,(1976), Moon Morphology, U.
e, B. R. et al. (2004), Icarus
et al. (2005), Icarus 176, 351al. (2006), J. Geophys. Res.
] Schultz P.H. (1988), Lunar
Houston, pp. 1039-1040; [7]S, 41, Issue 10, p.1539-1550;
07), Icarus 190, 295-333; [9]38, No. 1391; [10] Anderson,(2006), LPSC 37, abstract
d Gault D.E. (1984), J. Geo[12] Anderson, J. L. B. et al.

densitypact viewed fromlow
above(slightlysieved
uprange (left) and from theIn thisspeedcase,ejecta
the that will formside (right). Thisperlite.
captures highest
the cardioid (heart-shaped)
distal rays.
impact pointis on theuprange wall.

[Schultz et al., 2009]

Figure 4: Conceptual depiction for origin of cardioid ray
pattern that maps the migration of the flow-field center during excavation.

[private communication with S. Yamamoto]Figure 1: Farside

3° North/ 100° West

[Schultz, 1992]

Fig. 1. The effectof atmosphericpressure(density)on ejcctacmplaccmentfor ejectadeposits
with distalejectathinningwithoutidentifiableboundaries.
Targetsin
hypervclocity
impactsinto compacted
pumice.(a) At 0.25 bar, a distinctive
ejecta Figureslb and lc had a thin veneerof dry temperasprinkledon the surface.Allrampart(arrow)encircles
the craters.(b) At 0.5 bar,lobesof ejecta(arrow)extend impactswere0.635cm aluminumspheres
impactingfrom5.0 to 5.4 km/sunderan
over four radii from the crater rim. A narrow scouredmoat often developa argonatmo6phere.
Scalebarscorrespondto 10 cm.
adjacentto the raisedtim. (c) Near 1 bar, a radial patterncharacterizes
the inner

raisedcraterrim for pressures
above0.4 bar. Impactsundera 1 ejecta lobes. At higher pressures,the surface was visibly
bar atmosphereproduce an extensive,radially scouredejecta scoured.Nevertheless,containersplaced at different distances
depositwith a morepronounced
rim depression(Figurelc). In from the crater collectedonly minisculeamountsof ejecta

目的๏ ガラスビーズターゲットに衝突をさせ、実験条件（大気圧，衝突速度，粒径など）を変化させたときにどのようなエジェクタ地形ができるかを調べ，分類する
๏ 相図を描き、エジェクタ地形の形成条件を制約する

実験条件とパラメータ๏ 標的 : ガラスビーズ 100 µm (50, 420 µm)
๏ ターゲット準備状況 : well-packing / loose packing
๏ チェンバー内大気圧 : 102 Pa 〜 105 Pa (大気圧)๏ 衝突速度 : 数 〜 百数十 m/s
projectile

ambient

facilities

diametermassmaterialshape

impact velocity

pressure

25.0 mm63.6 gFe

spherea few m/s

atmos.

free fall

24.6 mm

19.2 gglass

spherea few m/s

atmos.

free fall

29.7 mm

39.1 gAlspherea few m/s

atmos.

free fall

24.5 mm67.4 gFespherea few m/s

102-105 Pa

free fall

9.53 mm

0.5 g

Nylon

sphere20 ~ 40 m/s

atmos.

gun in Nagoya

9.53 mm

0.5 g

Nylon

cylinder20 ~ 40 m/s

atmos.

gun in Nagoya

10 mm

6.0 g

Stainlesscylinder~ 50 m/s~ 103 Pa

gun in Kobe

10 mm

0.9 g

50 ~ 120 m/s

103-105 Pa

gun in Kobe

10 mm

2.1 g

50 ~ 120 m/s

103-105 Pa

gun in Kobe

Polycarbonate cylinder
Alcylinder

Results：
target mean
diameter

100 µmtarget initialcondition

wellpacking

ambient
pressure

103 Paimpactvelocity

52.8 m/s

recorded in 5000 fps

seminar nameseminar name

地形の分類Fine radial w/o concentric

Knobby radial w/o concentricRadial w/ regular concentric

Radial w/ thick concentric

Radial w/ wavy concentricDimpleNo morphologyターゲット準備状態による地形の違い

loose packing
target mean
diameter

100 µmtarget initialcondition-ambientpressure

105 Paimpactvelocity

well-packing

ビーズを流し込む

5.4 m/s

ビーズを流し込んだあと

Dimple Radial w/ regular揺する
concentric

大気圧による地形の違い
P=5.0x102 Pa

P=1.0x105 Pa

Radialw/ concentric
Radialw/o concentric
P=1.0x104 Pa

P=1.0x103 Pa

P=3.5x103 Pa

P=6.2x103 Pa

衝突速度による地形の違い
Radial w/wavy concentric
v = 83.8 m/s
Radial w/regular concentricv = 58.3 m/s

v = 38.9 m/starget mean
diameter

100 µmtarget initialcondition

wellpacking

ambient
pressure

105 Paimpactvelocity-Radialw/o concentric
v = 8.0 m/s

July, 2010 : ISSI, Bern

大気圧と衝突速度を用いた相図
updated 10.07.23

Radial + Thick concentric
Radial + Regular concentric
Radial + Wavy concentric
Knobby radial (No concentric)
Fine radial (No concentric)

target : glassbeads, d = 100µm, initially packed
projectile: Al (10 mm! x 10 mm),
Polycarbonate (10 mm! x 10 mm),
Stainless (10 mm! x 10 mm),
Carbonsteel sphere (25.4mm)

impact velocity [m/s]150

target mean
diameter

100 µmtarget initialcondition

wellpacking

ambient
pressure-

impactvelocity-

100

Dimple mode (loosepacking)

50？

？
0
2102

3 4 5 631050 µm : trend is similar
420 µm : no pattern2

3 4 5 6410target pressure [Pa]2

3 4 5 6510

concentric パターンRadius of crater and continuous ejecta (rampart)vs. impact velocity (concentric pattern)
140
120

Radius [mm]

100
8060
405Crater (P = 10 Pa)
5Cont. ejecta (rampart) (P = 10 Pa)
44Crater (10 < P < 5x10 Pa)
44Cont. ejecta (rampart) (10 < P < 5x10 Pa)

20
0020

40
60
Impact Velocity [m/s]80100

抗がかかる場合，運動方程式は，エジェクタ到達距離の簡易モデル

dvv
m= mg − k |v|2 ,dt|v|(1)v
くには数値計算する．しかしとりあえず簡単に解く．
，速度が速いときは効くが，遅くなれば影響は小さくなるはずxに比べて大きいときと小さいときに分ける．
ccve

Eureka, 10.11.20, 09:41

θL1

L2

Ayako Suzuki( &'&')
1
1!
"−1 !
"!
"2)√Pve
P 21vP1e∴ Ltotal = 0.200ln+ √ + * 2 ln+,555
101.67 101.67 1022ちなみに，P = 105 [Pa], ve = 55 [m/s] (100709exp05 の条件) を代入すると，(54)

モデルにおけるエジェクタの到達距離

concentric パターンRadius of crater and continuous ejecta (rampart)vs. impact velocity (concentric pattern)
140
120

Radius [mm]

100
80
60
40
5Crater (P = 10 Pa)
5Cont. ejecta (rampart) (P = 10 Pa)
4
4
Crater (10 < P < 5x10 Pa)
44Cont. ejecta (rampart) (10 < P < 5x10 Pa)

2000204060
Impact Velocity [m/s]80100Summary๏ 粒径による違い- 50, 100 µm -> Radial / Radial w/ concentric. / Dimple- 420 µm -> No morphology
๏ ターゲット準備状態による違い（大気圧下のみ）- well-packing (low porosity) -> Radial mode
- loose packing (high porosity) -> Dimple
๏ 相図を描いた- 大気圧，速度，粒径によって地形の違いができる๏ エジェクタ到達距離の簡易モデル- concentric パターンを作っているエジェクタは，かなり遅い速度で放出された- 大気圧による減速は実験では観測された．別の減速モデルの必要性