Rayed craters on planets
Kuiper, D=62 km

粉体への衝突現象で見られる
40th Lunar and Planetary Science Conference (2009)

エジェクタ地形の分類
2496.pdf

If this interpretation is valid, then arcuate uprange
crater rays not only reflect impact angle but also thethe projectile-to-crater diameter ratio. At laboratory 1
A.hypervelocity
Suzuki , T. Kadono2, M. Arakawa3, A. M. Nakamura1,scales, this ratio for sand is ~ 40 for
oblique (30°) impacts. At planetary scales (10’s ofK. Wada4, S. Yamamoto5km), it reduces to 15-20 but will depend on gravity,impactor density (target and projectile), as well as proSchool Sci., Kobe Univ.，2Inst. Laser Eng., Osaka Univ.,
jectile speed. For gravity-controlled craters1CPS/Grad.
of thesame size, the size of the impactor (65 km/s) producing 3
Grad. School Env. Studies, Nagoya Univ.，4PERC, Chitech,a crater on Mercury will be ~60% smaller than thesame-size crater on the Moon (23 km/s). For retroFigure 2: Oblique impact craters on Mars illustratingcar- Inst. Env. Studies
5National
grade comets impacting Mercury, the projectile will bedioid-shaped uprange (left) and composite crater, Dilly
two times smaller for the same size crater on the(right). The similarity with other ballistic ray patterns indiMoon. On Mars (12 km/s), however, the projectiles
cates for a curtain-driven vortex origin for the terminal ramnar and Planetary Science Conference(2009)
2496.pdf
should be ~45% larger. Consequently, the uprange rayparts. The small crater Dilly (2 km diameter) exhibits a lowpattern may provide clues to impactor type (cometthermal inertia (dark) distal arachnid ray pattern and a highversus asteroidal) for oblique impacts. Retrograde
thermal inertia proximal rim deposits. This suggests a lowcomets may have linear rays even though obliquedensity surface layer.
If this interpretation is valid, thenarcuateuprange(zones of uprange avoidance), whereas prograde astercrater rays not only reflect impact oids
angle
the cardioid rays. Oblique imwillbut
havealso
accentuatedFigure 3: Example ofpact crater on Mars should be characterized by thethe projectile-to-crater diameter ratio. At laboratory
cardioid shaped ray
uprange cardioid pattern due to lower impact speeds.
pattern uprange for anscales, this ratio for sand is ~ 40Low-density
for hypervelocity
surface materials (e.g., aeolian loess),
oblique hypervelocity
oblique (30°) impacts. At planetaryscales(10’sofin arachnid ray patterns (Fig.
however,shouldresult
impact (~ 5 km/s) into2b).
low density sievedkm), it reduces to 15-20 but will dependon gravity,
Consequently, arcuate ray patterns provide newperlite. In this case, theimpactor density (target and projectile),
as well as proimpact point is on theclues to the early-time cratering flow field and can beuprange wall.
jectile speed. For gravity-controlled craters invertedof theto provide conditions of impact.
same size, the size of the impactor (65 km/s) producing
Oberbeck, V. R. et al. (1974) Proc. Lunar Sci. Conf-, Sth,a crater on Mercury will be ~60%[1]smaller
thanthep. 111-136; [2] Schultz, P. H. (1976), Moon Morphology, U.
same-size crater on the Moon (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] McEwen
A. S., et al. (2005), Icarus 176, 351grade comets impacting Mercury, theprojectile
will bedioid-shaped uprange (left) and composite crater, Dilly
381; [5] Tornabene, L. L., et al. (2006), J. Geophys. Res.
two times smaller for the same sizecrater
onE10006;
the [6] Schultz(right).
similarity
with other ballistic ray patterns indi111(E10),
CiteID
P.H. The(1988),
Lunarand Planet.
Sci. XIX, LPI, Houston, pp. 1039-1040; [7]Moon. On Mars (12 km/s), 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;
should be ~45% larger. Consequently,
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. (comet(2008), LPSC 38, No. 1391; [10] Anderson,
pattern may provide clues to impactortypethermal inertia (dark) distalarachnidhigh- center durpatternthat mapsraythe patternmigration andof thea flow-field
J. L. B. and Schultz, P. H. (2006), LPSC 37, abstract
versus asteroidal) for oblique impacts.
Retrograde
ing
thermalinertiaJ. proximalrimexcavation.
deposits. This suggests a lowno.1726; [11] Schultz P.H. and Gault
D.E. (1984),
Geocomets may have linear rays evenobliquephys.thoughRes. 90, pp.
3701-3732; [12] Anderson, J. L. B. et al.
density surface layer.
(2003),MAPS 39, 303-320.
(zones of uprange avoidance), whereas
prograde
asteroids will have accentuated cardioid rays. Oblique imFigure 3: Example ofFigure 1: Farside
pact crater on Mars should be characterized by theMoon! The nature, origin, age, and formation processes havelong been the subject of major controversies [e.g.
Hawke et al., 2004]!"#"$#%$ Mercury&'()NASA/Johns Hopkins Univ. APL/Carnegie Inst. of Washington

12

目的Rays in the laboratory!Uprange ray pattern -- interpreted as an evolving
excavation flow field [Schultz et al., 2009]

lunar crater Jackson (71km diameter) exhibiting distinctive cardioid
uprange ray system
similar to Tycho.

uprange cardioid pattern due to lower impact speeds.
Low-density surface materials (e.g., aeolian loess),
however, should result in arachnid ray patterns (Fig.
2b).
Consequently, arcuate ray patterns provide newclues to the early-time cratering flow field and can beinverted to provide conditions of impact.

! ガラスビーズターゲットに衝突をさせ、実験条件を変化させたときにどのようなエジェクタ地形ができ

cardioid shaped ray
pattern uprange for an
oblique hypervelocity
impact (~ 5 km/s) into
Figure 5: Evolution of in-flight ejecta at 160 ms after imdensity
pact viewed fromlow
above(slightlysieved
uprange (left)
from100°
the West3°andNorth/
thisspeedcase,ejecta
the that will formside (right). Thisperlite.
captures In
highestthe cardioid (heart-shaped)
distal israys.
impact pointon theuprange wall.

るかを調べ、分類すること! 相図を描き、各エジェクタ地形の形成条件を制約す[Schultz et al., 2009][1] Oberbeck, V. R. et al. (1974) Proc. Lunar Sci. Conf-, Sth,p. 111-136; [2] Schultz, P. H. (1976), Moon Morphology, U.
Texas press, 628pp; [3] Hawke, B. R. et al. (2004), Icarus
170, 1-16; [4] McEwen A. S., et al. (2005), Icarus 176, 351381; [5] Tornabene, L. L., et al. (2006), J. Geophys. Res.
111(E10), CiteID E10006; [6] Schultz P.H. (1988), Lunarand Planet. Sci. XIX, LPI, Houston, pp. 1039-1040; [7]Wrobel, K. et al. (2006), MAPS, 41, Issue 10, p.1539-1550;[8] Schultz, P. H., et al., (2007), Icarus 190, 295-333; [9]Herrick, R. et al. (2008), LPSC 38, No. 1391; [10] Anderson,J. L. B. and Schultz, P. H. (2006), LPSC 37, abstract
no.1726; [11] Schultz P.H. and Gault D.E. (1984), J. Geophys. Res. 90, pp. 3701-3732; [12] Anderson, J. L. B. et al.
(2003), MAPS 39, 303-320.

ること[private communication with S. Yamamoto]Figure 4: Conceptual depiction for origin of cardioid ray
pattern that maps the migration of the flow-field center during excavation.
34

Figure 1: Farside
lunar crater Jackson (71km diameter) exhibiting distinctive cardioid
uprange ray system
similar to Tycho.

Figure 5: Evolution of in-flight ejecta at 160 ms after impact viewed from above (slightly uprange (left) and from theside (right). This captures highest speed ejecta that will form
the cardioid (heart-shaped) distal rays.

実験条件とパラメータ

ターゲット準備状態による地形の違い! 標的 : ソーダライムガラスビーズ (50, 100, 420 !m)! パラメータ- 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
diametermass

25.0 mm63.6 g29.7 mm

39.1 g24.6 mmprojectile
materialFe9.53 mm

0.5 g

10 mm
10 mm

6.0 g
0.9 g
2.1 g

atmos.

sphere67.4 g10 mm

a few m/s

Al24.5 mm0.5 g

impact velocity

sphereglass

9.53 mmshapesphereFe19.2 g

Nylon
Nylon

StainlessspherespherecylindercylinderPolycarbonate cylinder
Alloose packing
ambient
pressurecylindera few m/s
a few m/s

atmos.

102-105 Pa

20 ~ 40 m/s

atmos.

20 ~ 40 m/s~ 50 m/s

50 ~ 120 m/s
50 ~ 120 m/s

free fall
free fall
free fallatmos.

gun in Nagoya~ 103 Pa

gun in Kobe

103-105 Pa
103-105 Pa

well-packing

free fallatmos.

a few m/s

facilities

gun in Nagoya
gun in Kobe

Dimple Radial w/ regular concentricgun in Kobe
5大気圧による地形の違い
P=5.0x102 Pa

6

衝突速度による地形の違い
P=1.0x105 Pa

Radial w/
wavy concentric
v = 83.8 m/s

Radialw/ concentric

Radial w/
regular concentric

Radialw/o concentricv = 58.3 m/s
P=1.0x104 Pa

P=1.0x103 Pa

P=3.5x103 Pa

v = 38.9 m/s

P=6.2x103 Pa
7target mean
diameter

100 !mtarget initialcondition

wellpacking

ambient
pressure

105 Paimpactvelocity-Radialw/o concentric
v = 8.0 m/s*+,-.!%"!"!/ 0110.!2345
8大気圧と衝突速度を用いた相図
updated 10.07.23
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

updated 10.07.22

target mean
diameter

100 !mtarget initialcondition

wellpacking

ambient
pressure-impact
velocitytarget : glassbeads, d = 50µm, initially packed
projectile: Al, 10 mm!! x 10 mm

Radial + Wavy concentricFine radial (No concentric)-

100

Dimple mode (loosepacking)

50？

？
02102

3 4 5 63102

3 4 5 64102

3 4 5 6target mean
diameter

50 !mtarget initialcondition

wellpacking

ambient
pressure-

impactvelocity-150

impact velocity [m/s]

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

100

5050 µm : trend is similar
420 µm : no pattern

0210510234 5 6103234 5 6410234 5 6105

target pressure [Pa]target pressure [Pa]
910

地形の分類

Knobby radial w/o concentric

updated 10.07.22
target : glassbeads, d = 420
100µm, initially packed
projectile: Al, 10 mm!" x 10 mm

ModeD No morphology (target = 420 !m)impact velocity [m/s]

150100target mean
diameter

420 !mtarget initialcondition

wellpacking

ambient
pressure-

impactvelocity-

Fine radial w/o concentric

50

02102

3 4 5 631023 4 5 61042

3 4 5 6510

target pressure [Pa]1112Dimple

Radial w/ thick concentric
Radial w/ regular concentric

Radial w/ wavy concentric
1314Summary! 粒径による違い- 50, 100 !m -> Radial / Radial w/ concentric. / Dimple- 420 !m -> No morphology! ターゲット準備状態による違い（大気圧下のみ）

No morphology- well-packing (low porosity) -> Radial mode
- loose packing (high porosity) -> Dimple! 相図を描いた- 粒径、衝突速度、大気圧によってエジェクタ地形は異なる

1516