衝突論文セミナー 15分発表
2009.10.13 豊田丈典 (東大地震研, D1)

気になる論文 2009“Distribution of Mid-Latitude Ground Ice on Mars from New
Impact Craters”, Byrne et al., Science”Latitude dependence of Martian pedestal craters: Evidence for asublimation-driven formation mechanism”, Kadish et al., JGR“One-handred-km-scale basins on Enceladus: Evidence for an
active ice shell”, Schenk and McKinnon, GRL“Compaction experiments on ice-silica particle mixtures:
Implication for residual porosity of small icy bodies”, Yasui andArakawa, JGR

気になる論文 2009
“Results from the Mars Phoenix Lander Robotic Arm
experiment”, Arvidson et al., JGR“Data’s shameful neglect”, Nature“The rate of granule ripple movement on Earth and Mars”,
Zimbelman et al., Icarus“Machine cataloging of impact craters on Mars”, Stepinski et al.,Icarus気になる論文 2009

“A redetermination of the ice/vapor ratio of Enceladus’ plumes:
Implications for sublimation and the lack of a liquid water
reservoir”, Kieffer et al., Icarus

“Distribution of Mid-Latitude Ground Ice on Mars from New Impact
Craters”, Byrne et al., Science
REPORTS
Fig. 2. HiRISE falsecolor data (see Table
1 for image details)
showing sublimation oficy material at site 1.
Panels are 75 m across.
Images here and in Fig. 3
have north at the top
and are illuminated fromthe lower left. Plot shows
the brightness evolutionof the lower-right icy
patch (solid) and dark
impact zone (dashed) ineach HiRISE filter scaledby the brightness of the surrounding undisturbed terrain (to remove incidence angle and first-order atmospheric effects). Vertical lines show observation dates. Bluegreen and near-infrared bands at Ls 126° were summed 4 × 4.
Fig. 3. HiRISE false-color data ofsites 2 to 5 (see Table 1 for image
details). Left panels are 35 m across;gridlines at site 3 show the scale(18 m) (but not location) of CRISM
pixels. CRISM spectrum at lower
right with water ice absorption

ly drain through the ejecta blanket or heavily
fractured crater floor.
These craters formed near the abrupt transition from where ground ice is expected to bestable to where it is not (Fig. 1). Here, the expected depth to ice in models is very sensitive tohave north at the top
and are illuminated fromthe lower left. Plot shows
the brightness evolutionof the lower-right icy
patch (solid) and dark
impact zone (dashed) ineach HiRISE filter scaledby the brightness of the surrounding undisturbed terrain (to remove incidence angle and first-order atmospheric effects). Vertical lines show
green and near-infrared bands at Ls 126° were summed 4 × 4.

“Distribution of Mid-Latitude Ground Ice on Mars from New Impact
Craters”, Byrne et al., ScienceFig. 3. HiRISE false-color data ofsites 2 to 5 (see Table 1 for image
details). Left panels are 35 m across;gridlines at site 3 show the scale(18 m) (but not location) of CRISM
pixels. CRISM spectrum at lower
right with water ice absorption
bands indicated is an average offour adjacent pixels in observation
FRT0000D2F7.

Site 2: Ls 160˚

Site 4: Ls 149˚

Site 5: Ls 160˚
(nominally 2.5 m s−1) and initial ice albedo

Single-scattering Albedo

Site 3: Ls 151˚

Microns

indicating that atmospheric dust is settling out only drain through the ejec
fractured crater floor.
These craters formed ntion from where ground i
stable to where it is not (pected depth to ice in modlatitude (fig. S4), and its precraters provides a strong
Results of models using 20
water vapor (9) agree very
our data (whereas ground i
expected with 10 pr-mm)
1 appear to have exposed t
and their depths coincide
pected ice-table depth. Sit
depths exceeding the modground ice; excavation ofwith model results (depth cfor site 3; however, 8-m cra
The Phoenix lander enc
cemented soil and clean ic
at depths close to model pr
Lander 2 (Fig. 1) dug tren
48°N (26) and did not dis
predicts ice at 24 cm). Giv
is likely that ice exists her
excavated to in the 1970s.
The highest-latitude i”Latitude dependence of Martian pedestal craters: Evidence for asublimation-driven formation mechanism”, Kadish et al., JGR
E10001

KADISH ET AL.: LATITUDE DEPENDENCE OF PEDESTAL CRATERS

E10001

E10001Figure 5. Examples of typical pedestal craters shown in THEMIS VIS data with MOLA altimetry data.
Each image has a MOLA track consisting of the shot data, corresponding to a topographic profile seen in

KADISH ET AL.: LATITUDE DEPENDENCE OF PEDESTAL CRATERS

Figure 6. The topographic profiles for the pedestal craters shown in Figure 5, with visible data points
corresponding to the MOLA shot data. Vertical exaggerations for each of the profiles are (a) 65X, (b) 55X,(c) 50X, and (d) 47X. Pedestal heights vary from !50 to 75 m. Pedestal surfaces are extremely flat, withslopes generally <1!, and pedestal scarps have slopes of <5!. In all cases, the crater cavity is entirely above
the elevation of the surrounding plains. In some cases (Figures 6a and 6d), infilling of the crater bowl or
lowering of the pedestal surface causes the crater floor to be above the height of most of the surrounding
pedestal as well.

E10001

”Latitude dependence of Martian pedestal craters: Evidence for asublimation-driven formation mechanism”, Kadish et al., JGR
E10001

KADISH ET AL.: LATITUDE DEPENDENCE OF PEDESTAL CRATERS

E10001

“One-handred-km-scale basins on Enceladus: Evidence for an active
ice shell”, Schenk and McKinnon, GRL
Figure 1. Partial global stereo-derived DEM of Enceladus. Dark is low and bright is high elevation, blank unmapped.
L16202

Dynamicof topography shown is 2 km. CurvedL16202
black outline shows extent of older cratered terrains. Heavy lines
SCHENK AND MCKINNON:
BASINSrange
ON ENCELADUS
show locations of profiles in Figure 2. White letters are basins listed in Table 1, south polar depression is the darker greyzone south of $60!S. Global cylindrical map projection centered on 0!N, 180!W.
rocky core surrounded by an icy mantle !80-to-100-km
thick [Schubert et al., 2007; Barr and McKinnon, 2007].
The small size and low surface gravity of Enceladus allow
for potentially large variations in core topography and thus
geoid shape at the satellite surface (the geoid goes as 1/g,
where g is surface gravity [0.11 m s"2 for Enceladus], so thehydrostatic surface deflection for a given mass anomaly is
100# that on the Earth). However, the limited horizontal
scale of the Enceladus basins requires uncompensated mass
anomalies much closer to the surface than any plausible
rocky core (see Auxiliary Material). In this case, though, themagnitudes of the required mass anomalies are too large tobe plausible within an icy shell, so we reject geoid variation
as an explanation.

vertical length scale h in Enceladus’ ice shell gives rise to athermal buoyancy stressszz $ rgadTh ¼ 5

dT
10 K

!

"!

"
h
kPa;
25 km

ð1Þ

where r and a are the density and volume thermal
expansion coefficient of ice, respectively, and !10 K is
the rheological temperature scale (over which the viscosity
varies by e) for diffusion creep. Even for an $25 K
variation across the entire upper convective thermalboundary layer (see scaling of Solomatov and Moresi[2000]), (negative) buoyancy stresses within Enceladus are

3.2. Dynamic Topography[7] If the south polar terrain is related to upwelling, as insome models [McKinnon and Barr, 2007; Barr, 2008; Tobie
et al., 2008], then downwelling probably occurs elsewhere.
Convection in the ice shell driven by internal heating or ocean
is possible
Enceladusand McKinnon,
2007;
Figure 1. Partial global stereo-derived DEM of Enceladus.cooling
Dark islow andfor
brightis high[Barrelevation,
blank unmapped.
RobertsandNimmo,
2008].
Following
Barr
and
McKinnonDynamic range of topography shown is 2 km. Curved black outline shows extent of older cratered terrains. Heavy lines[2007],
anomalyof amplitude
over greyashow locations of profiles in Figure 2. White letters are basinslisteda inthermal
Table 1,south polar
depressiondTisacting
the darker
zone south of $60!S. Global cylindrical map projection centered on 0!N, 180!W.
Table 1. Topographic Depressions on Enceladus

rocky core surrounded by an icy mantle !80-to-100-km Basinvertical Latitudelength scaleLongitude
h in Enceladus’ice(km)shell gives
rise
to a
Width
Depth
(km)
thick [Schubert et al., 2007; Barr and McKinnon, 2007]. A thermal buoyancy
stress
15!S
155!W
140 # 175
1.5
The small size and low surface gravity of Enceladus allow B
15!N
225!W !
0.8 – 1"$100!
"
dT $90 h
for potentially large variations in core topography and thus C
30!N
190!W
$1
kPa; $1 ð1Þ
szz $ rgadTh
¼5
28!N
300!W
geoid shape at the satellite surface (the geoid goes as 1/g, D
10 K $140
25 km
45!N
215!W
$130
1.25
where g is surface gravity [0.11 m s"2 for Enceladus], so the E
F
50!N
350!W
$150
$1
Figure 2. Topographic profiles across one of the largehydrostatic surface deflection for a given mass anomaly is SPD
where r$90!S
and a are0!W
the density
300 –and350 volume
0.4 thermal– 0.8
100# that on the Earth). However, the limited horizontal expansion coefficient of ice, respectively, and !10 K is basins (A) shown in Figure 1.
scale of the Enceladus basins requires uncompensated mass the rheological temperature scale (over which the viscosity

“Compaction experiments on ice-silica particle mixtures:
Implication for residual porosity of small icy bodies”, Yasui andArakawa, JGR
Click
Here

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, E09004, doi:10.1029/2009JE003374, 2009

for

Full
ArticleCompaction experiments on ice-silica particle mixtures: Implication
for residual porosity of small icy bodies
Minami Yasui1 and Masahiko Arakawa1
Received 5 March 2009; revised 11 June 2009; accepted 22 June 2009; published 22 September 2009.

[1] To evaluate the residual porosity of small icy bodies, we performed compaction

experiments on ice-silica mixtures and studied the effects of silica content, temperature,and compaction time scale on residual porosity. To simulate the compositions of real icy
bodies, we used ice-silica mixtures with different silica volume fractions (0–0.29). The
mixtures were compacted at a constant compression speed of 0.2 or 2.0 mm/min and thetemperature was set to !10!C or a lower temperature (from !55 to !67!C). For the!10!C case, the mixtures were compressed to pressures of 30 MPa, while the lower
temperature measurements were compressed to 80 MPa. In both cases, the residual
porosity was found to be larger for higher silica fractions. At !10!C and 30 MPa, theresidual porosity varied from 0.01 to 0.14 for silica fractions of 0–0.29, whereas for the !55
to !67!C and 80 MPa case, the corresponding residual porosities were 2–10 times
larger. A two-layer model was proposed to calculate the compaction curves of ice-silica
mixtures from the curves of the corresponding pure materials. We estimated the residual
porosity of small icy bodies using this two-layer model. From our calculations, we expectthat icy bodies with diameters smaller than 700 km have residual porosity larger than
0.3 when the temperature is lower than !55!C.

Citation: Yasui, M., and M. Arakawa (2009), Compaction experiments on ice-silica particle mixtures: Implication for residual
porosity of small icy bodies, J. Geophys. Res., 114, E09004, doi:10.1029/2009JE003374.

1. Introduction

et al., 2006]; this difference could be attributed to theing excavations in the RA work volume along with TECP
rated from SSI image data.

soil
ons
nd a
nce
ased
pecth a
and
h et
the
n to
y of
ing,
al at

uthand
ion.
and
wall,
soil
area
nce
eterody
een
ned,
ly a
tent
s of

“Results from the Mars Phoenix Lander Robotic Arm experiment”,
Arvidson et al., JGR

microscopic imaging and AFM measurements (Goetz,
submitted manuscript, 2009). This material looked similar
Figure 9. (left) The state of the Snow White trench and associated three dump piles (Croquet Ground)on sol 45 after extensive RA operations to make the excavation three scoops in width (scoop is 8.5 cm
to the sand and silt-sized soils acquired from other sites,wide). The chatter marks are associated with pulling the titanium blade across the hard icy soil surface
with more sand size grains thought to have been roundedencountered at !3 – 5 cm depth. The dark surface on the left portion of the trench is interpreted to be
newly exposed icy soil. Note the cloddy nature of the soil in the dump piles and the steep trench walls.
during aeolian saltation transport.
The horizontal brightness variations on the trench back wall are due to ISAD impressions and are notindicators of soil layering. (right) The trench extended toward the Lander to make more room for rasping,
the effects of scraping (tungsten carbide blade) that leave dark striations, and two test rasp holes
excavated on sol 50 (acquired on sol 51). The imprints of the cleated surface that surrounds the rasp holes
is also evident. SSI images SS045IOF900218735_15030R2M1 (color includes exposures RC, RB, RA,
R1, and R8) and SS051IOF900727652_15BE0RCM1 (color exposures RB, RA, and R1).

Figure 10. Color view of Snow White and associated trenches on sol 72, 8 sols after a sample was
successfully delivered to the TEGA-0 from icy soil acquired from the array of 16 rasp holes evident in theimage and left to sublimate some of the icy component. Rosy Red sample sites are shown on the left and arelocations for samples of surface soil, down to !2.5 cm depth. The debris sitting on the end wall and upper
trench is a consequence of trying to use the titanium blade to cut a vertical wall to search for texturalvariations in soil properties. SSI image SS072IOF902591122_182C0L2M1 (and exposure L1).

Figure 6. Color view acquired on sol 19 showing icy soilin the Dodo-Goldilocks trench, together with the Caterpillar

13 of 21

“Data’s shameful neglect”, Nature
www.nature.com/nature

Data’s shameful neglect

Vol 461 | Issue no. 7261 | 10 September 2009

Research cannot flourish if data are not preserved and made accessible. All concerned must act accordingly.

M

ore and more often these days, a research project’s success ismeasured not just by the publications it produces, but also by
the data it makes available to the wider community. Pioneering archives such as GenBank have demonstrated just how powerfulsuch legacy data sets can be for generating new discoveries — especially when data are combined from many laboratories and analysedin ways that the original researchers could not have anticipated.
All but a handful of disciplines still lack the technical, institutionaland cultural frameworks required to support such open data access(see pages 168 and 171) — leading to a scandalous shortfall in the
sharing of data by researchers (see page 160). This deficiency urgently
needs to be addressed by funders, universities and the researchers
themselves.
Research funding agencies need to recognize that preservation ofand access to digital data are central to their mission, and need tobe supported accordingly. Organizations in the United Kingdom,
for instance, have made a good start. The Joint Information Systems
Committee, established by the seven UK research councils in 1993,

also the software that will help investigators to do this. One important facet is metadata management software: tools that streamline
the tedious process of annotating data with a description of what thebits mean, which instrument collected them, which algorithms havebeen used to process them and so on — information that is essential
if other scientists are to reuse the data effectively.
Also necessary, especially in an era when data can be mixed andcombined in unanticipated ways, is software that can keep track ofwhich pieces of data came from whom. Such systems are essential if
tenure and promotion committees are ever to give credit — as theyshould — to candidates’ track-record of“Data management
data contribution.
Who should host these data? Agencies should be woven
and the research community together into every course inneed to create the digital equivalent science.”of libraries: institutions that can takeresponsibility for preserving digital data and making them accessible
over the long term. The university research libraries themselves arere flags into the crests of several granule
the survey line. When the surveying wasised to see that a 3-cm-high granule ripple
ss than 2 h (Fig. 3a). A visit to the site thewed us to document the movement of aule ripple over a period of 23 h (Fig. 3b).
the flags on the smaller granule ripples
fallen over due to the complete dispersal
but the flags remained in place in the lard failure of two digital cameras resulted ing. 3 being the only ones for which usefule derived.

10 & 10$5 kg m$1 s$1 for the 3-cm-high and 10-cm-high GSDNPP
granule ripples, respectively. We interpret this favorable comparison to indicate that the saltation-induced granule creep flux conditions at GSDNPP and WSNM were quite comparable.
Continuity of shape for the moving GSDNPP granule ripples
indicates that the advancing lee side of the ripple sweeps out a parallelogram. The area of this parallelogram is equal to the ripple
height times the horizontal length of the crest movement. The parallelogram produced by the advancing ripple lee face can be related to the volume of granules transported over the crest byconsidering all values to be normalized per unit crest length. The
volume estimate assumes that the granules on the advancing lee“The rate of granule ripple movement on Earth and Mars”,
Zimbelman et al., Icarus

74

J.R. Zimbelman et al. / Icarus 20

4. R

tion
ma
ave
rip
are
ber
sho
tra
of i
line
flag
the
10-

J.R. Zimbelman et al. / Icarus 203 (2Fig. 2. Wind data for period that flags were in place on granule ripples at GSDNPP.
Light grey line indicates 5 m s$1, the saltation threshold wind speed at 1 m height.
The ripples shown in Fig. 3 were both flagged at 0 time on the plot. Data are fromthe Alamosa airport, located 45 km SSW of study site, representative of a height
well above 1 m (from NCDC).

flux

respeconlent satime
qcp¼
is supwhmovedrat
indicatobs
drivenheight
(=1
wind
ples
with
a cfl
the weav
seems
val
ation. T
10
ple cregra
mass fleterson
an
tion
mass
fl
creep mnight, and well above threshold throughout all of the daylight
hours (Fig. 2). The NCDC data documented that the strong winds
were consistently from an azimuth of between 190! and 230!
(measured clockwise from north) when the wind speed was above
threshold. Prior to conducting the survey along the recovered line,
one of us (RI) placed wire flags into the crests of several granuleripples within !20 m of the survey line. When the surveying wascomplete, we were surprised to see that a 3-cm-high granule ripple
had clearly moved in less than 2 h (Fig. 3a). A visit to the site thecrests, GSDNPP. (a) Photo taken 109 min after flag was placed on crest, indicating 2.1 cm movement (to left)
3-cm-highripple.
Fig.of
4. theTopographic
profilesurveyedacrossthreelarge granuleat GSDNPP of(a afollowingmorning
allowedus
toSmaller
document
theripples
movement
local slope of 1.5! has been removed). The surveyed ripples are part of an extensive
nearby10-cm-highgranulerippleovera period of 23 h (Fig. 3b).
ind
d ripples are in the background. Wind intensity ripped the flag material, which is 6.7 cm along the wire. JRZ,
9/15/06.
(b)
Photo
taken
1380
min
granule ripple field; the surveyed ripples are #20 m WNW of the flagged granule
By ripples
September
16, theallmarginof theflags
onwire.
the field.
smaller
granuleripplesalle3) alongof thegranulerippleVerticalexaggerationisof a different ripple than that shown in (a)), indicating 10.5 cm movement (to right) of the 10-cm-high ripple.
Flag (Fig.
material
is
6.7
cm
along
26.6!.
(such
as in Fig. 3a) had fallen over due to the complete dispersal 5. App
hei“Machine cataloging of impact craters on Mars”, Stepinski et al.,Icarus80

T.F. Stepinski et al. / Icarus 203 (2009) 77–87

82

T.F. Stepinski et al. / Icarus 203 (2009) 77–87

Fig. 3. Craters identified by the AutoCrat system in the Terra Cimmeria 1 site (top left), the Terra Cimmeria 2 site (bottom left), the Terra Cimmeria 3
Terra Cimmeria 4 site (bottom right). The background shows the topography; high-to-low areas are depicted by dark-to-light grays.

Fig. 1. Identification of crater candidates from topographic data. (Left) Topography of the Tisia Valles site on Mars. (Center left) Three optimized landscapes (layers)
corresponding to k1 , k2 and k3 , respectively. (Center right) Unexpanded depressions identified in the first three layers. (Right) Expanded depressions that passed the verification
test.

(or semi-automatic) pattern recognition in data (Witten and Frank,
2000). In our context data is the list of crater candidates and we arefocusing on classification learning (also known as supervised learning)—a scheme that ‘‘learns” how to classify crater candidates intoeither a crater class or a non-crater class from a set of previouslyclassified examples (called a training set). Each crater candidate
has been assigned a list of numerical attributes (see the previous
sub-section). We use these attributes to derive a shorter list of classification attributes fD; d; d=D; m ; m ; classg for use by the ma-decision tree constructed by the C4.5 algorithm on the basis of
431 examples in the C kPk3 training set. The tree has 15 nodes and8 leaves (terminal nodes). Feeding this tree with an unlabeled crater candidate detected in C kPk3 layers determines whether the candidate is a crater (terminal nodes denoted by 1) or non-craterfeature (terminal nodes denoted by 2) with expected accuracy of
89%. Accuracy is measured using 10-fold cross-validation method
Fig. 4. Craters identified by the AutoCrat system in the Hesperia Planum site (left) and the Sinai Planum site (right). The background shows the topogr(Kohavi, 1995). Fig. 2 (left) showsarea depicted
decisiontree constructed onby dark-to-light grays.
the basis of 1010 examples in the C training set. The tree has

S.W. Kieffer et al. / Icarus 203 (2009) 238–241

Ice - Water - Steam

400

C.P. B

650

5

1.0 x 10 Pa

350

550

77.2 Pa

250

500

2.7 Pa200

Temperature [°C]600

612 Pa

300

L

150

450

L+V

V

-2

3.3 x 10 Pa

400

100
50

S+L

0

L/V = 4.00 1.50

0.67 0.25

C

A

-150
-3

A'

S

S+V

I/V = 9.0

-1

1

3

5

7

V

1.0

1.5

4.0

9

0.6

11

250

220 K

D'

C'

B'

300

273 K
250 K

D

-50
-100

350

-6

1.6 x 10 Pa

13

15

Temperature [K]240“A redetermination of the ice/vapor ratio of Enceladus’ plumes:
Implications for sublimation and the lack of a liquid water reservoir”,
Kieffer et al., Icarus

190 K

200

145 K

150

0.4

0.2

0.1

17

19

21

100
23

Entropy [kJ/kg-K]
Fig. 1. Temperature–entropy diagram for H2O. S = solid (ice), L = liquid and V = vapor. Combinations of these indicate the L + V, S + V and S + L two-phase fields. CP is thecritical point. Green lines are lines of constant pressure, and blue lines are lines of constant mass ratio: I/V denotes the ice/vapor ratio; L/V denotes the liquid/vapor ratio. Data
below "100 !C are extrapolated (dashed lines) from the lowest temperature measurements available. The thermodynamic paths A–A0 , B–B0 , C–C0 and D–D0 are discussed in
the text.