(1) S. Silvestro, (2,3) D.A. Vaz, (4) G. Di Achille, (1) C ... · CV 0.76 1.26 1.11 0.73 Wavelength...
1
6.5° W 6° W 5.5° W 1.5° S 2° S 2.5° S TAR-streaks / 10 km ESA ExoMars 2016 landing ellipse Opportunity HiRISE HiRISE stereo Fig. 2e Fig. 2c Fig. 2d Fig. 2f-g Depression 300 m / 25 m 150 m 50 m 50 m 50 m 25 m 0.1 0.2 0.3 0.4 0 90 180 270 a c d TAR pop. 2b 2a 2b TAR-streak Fig. 2a TAR pop. 2a TAR pop. 1 TAR pop. 2b TAR pop. 2a TAR pop. 1 TAR pop. 1 TAR pop. 2b (streak) Pop. 3 f Pop. 3 Pop. 2b Pop. 2a Pop. 1 TAR pop. 2a TAR pop. 2b Pop. 3 -1886 -1889 Elevation (m) N b e g Depression 1 10 100 1000 0.01 0.1 1 10 25 50 75 90 99 99.9 99.99 Length (m) Probability (cum. %) Probability plot for Lognormal distribution 1 10 100 1000 0.01 0.1 1 10 25 50 75 90 99 99.9 99.99 Wavelength (m) Probability (cum. %) Probability plot for Lognormal distribution TAR pop. 1 TAR pop. 2 Bedform pop. 3 Subpop. 2b Subpop. 2a a) b) B, TAR pop. 2 (a & b, TAR-streaks formation) A, Bedform pop. 3 C, TAR pop. 1 ? Wind regime Wind regime Wind regime ? ? Pop. 3 S.pop. 2b S.pop. 2a Pop. 1 Mean azimuth (°) N STD (°) 3897 32.7 16.9 1618 17 39.5 2.4 11580 9.8 5341 85.3 32.9 Trend Length Mean (m) 7.8 36 20.4 108.5 STD (m) 35 2077.7 518.3 6273.2 CV 0.76 1.26 1.11 0.73 Wavelength Mean (m) STD (m) CV 5.4 15 2 29 6.3 50.6 0.5 114.7 0.47 0.47 0.33 0.37 Three episodes of aeolian construction have been identified visually (Figure 2) and statistically [1] (Figure 3) in the 2016 ESA ExoMars lan- ding site (Figure 1) suggesting that Meridiani Planum had a complex history of erosion end deposition triggered by different wind regi- mes (Figure 4) (see also [2]). The three bedform populations are: 1) TAR population 1 (Figure 2a-c), located inside craters, consists of NE-SW trending bedforms lying stratigraphically on top of the TAR population 2. 2) TAR population 2 (Figure 2a-e) can be divided in two different subclasses: 2a) large reticulate TARs (ladderback) [3,4,5] with three/two classes of crestlines (Figure 2c) with the main crestlines trending N-S (Figure 2b, Table 3b). The high directional variability characterizing trend measurements (Table 3b) suggests a strong topogra- phic control; 2b) smaller wavelength TARs (Table 3b) which can be found in continuity (Figure 2c and inset) or stratigraphically below the subpop. 2a (Figure 2d). This population is mainly located on the plain and has a similar trend to the subpop. 2a (Figure 2b). We also noticed two new important things: I) the occurrence of these bedforms is strongly topographically controlled as they clu- ster in the lee of impact craters forming a new type of wind streaks, the TAR-streaks (Figures 1, 2c inset, 2e). These streaks have an east to west direction suggesting they were formed by strong easterlies; II) the megaripples [6,7] are grouped in bands defining an older E-W orientation which we interpreted as a relict bedform pattern, the population 3 (Figure 2e-g). 3) Bedform population 3 appears as an alternating bright/dark banding on HiRISE images (Figure 2e, f). The paleo bedforms trend E-W (Figure 2b) and are locally influenced by the presence of depressions such as old eroded impact craters (Figure 2e). The paleobedform signature is locally erased by the TAR-streaks occurrence (Figure 2e). Y junction terminations are common (Figure 2f) and DTM analysis shows that these features have a clear topographic expression (~1-1.5 meters high, Figure 2f, g). FIGURE 2, BEDFORM PATTERN GROUPS FIGURE 3, BEDFORM PATTERN MEASUREMENTS FIGURE 4, GEOMORPHIC BACKSTRIPPING Different generations of aeolian bedforms give rise to the observed complex pattern. Bedform pop. 4 might represents a relict linear or transverse (zibars?) dune pattern. Pops. 1 and 2 were likely emplaced by uni-directional winds. Bedform surface induration/cementation likely followed each constructional stage favouring the development of the complex pattern ESA 2016 landing el- lipse in Meridiani Planum. HiRISE ima- gery and stereo deri- ved topography have been used to study aeo- lian bedform mor- phology (background: nighti- me THEMIS IR mosaic) Affiliations: (1) INAF Osservatorio Astronomico di Capodimon- te - Napoli (Italy), (2) Centre for Geophysics University of Coim- bra (Portugal), (3) CERENA, Lisbon (Portugal), (4) INAF - Osser- vatorio Astronomico di Collurania - Teramo (Italy) References: [1], Ewing et al. (2006), ESP&L; [2]Fenton et al. (this session); [3], Reddering (1987), Sedimentology; [4], Ramsay et al. (1989), Marine Geology; [5], Rubin et al. (2012), GSA meeting abst.; [6]Sullivan et al. (2005), Nature; [7], Golombek et al. (2010), JGR to be submitted...soon a) TAR pops.1 & 2, b) circular distributions of the bedform crestline trend for the three pops. identified c) TAR pops. 1 & 2 and location map (TAR streak - inset) d) locally the TAR subpop. a is found on top of subpop. 2b e-f-g) bedform pop. 3 which has a clear signature in the DTM rising 1-1.5 meters above the ground, g) 3D perspective of the orthoimage in panel f (10x v.e.) a) cumulative log frequency plots of crest spacing and length [1], note the inflection in the wavelength measurements marking the two subpopulations a and b (red line) b) main statistic parameters of the three populations identified FIGURE 1, STUDY AREA & METHOD EVIDENCE FOR DIFFERENT EPISODES OF AEOLIAN COSNTRUCTION IN THE 2016 EXOMARS LANDING SITE IN MERIDIANI PLANUM (MARS) (1) S. Silvestro, (2,3) D.A. Vaz, (4) G. Di Achille, (1) C. Popa and (1) F. Esposito ([email protected])
Transcript of (1) S. Silvestro, (2,3) D.A. Vaz, (4) G. Di Achille, (1) C ... · CV 0.76 1.26 1.11 0.73 Wavelength...
6.5° W 6° W 5.5° W
1.5° S
2° S
2.5° S
TAR-streaks
/
10 km
ESA ExoMars 2016 landing ellipse
Opportunity
HiRISE
HiRISE stereo
Fig. 2e Fig. 2c
Fig. 2d
Fig. 2f-g
Depression
300 m
/
25 m
150 m
50 m
50 m50 m
25 m
0.1
0.2
0.3
0.4
0
90
180
270
a c d
TAR pop. 2b
2a
2b
TAR-streak
Fig. 2a
TAR pop. 2a
TAR pop. 1
TAR
pop.
2b
TAR pop. 2a
TAR pop. 1
TAR pop. 1
TAR pop. 2b(streak)
Pop. 3
f
Pop. 3Pop. 2bPop. 2aPop. 1
TAR pop. 2aTAR pop. 2b
Pop. 3
-1886
-1889
Elevation (m)
N
b
e
g
Depression
1
10
100
1000
0.01 0.1 1 10 25 50 75 90 99 99.9 99.99
Leng
th (m
)
Probability (cum. %)
Probability plot for Lognormal distribution
1
10
100
1000
0.01 0.1 1 10 25 50 75 90 99 99.9 99.99
Wav
elen
gth
(m)
Probability (cum. %)
Probability plot for Lognormal distribution
TAR pop. 1TAR pop. 2Bedform pop. 3
Subpop. 2b
Subpop. 2a
a)
b)
B, TAR pop. 2 (a & b, TAR-streaks formation)A, Bedform pop. 3 C, TAR pop. 1
?
Windregime
Windregime
Windregime
?
?
Pop. 3S.pop. 2bS.pop. 2aPop. 1
Mean azimuth (°)N STD (°)
3897 32.7 16.91618 17 39.5
2.411580 9.85341 85.3 32.9
Trend Length
Mean (m)
7.836
20.4108.5
STD (m)
352077.7518.3
6273.2
CV
0.761.261.110.73
Wavelength
Mean (m) STD (m) CV
5.4152
29
6.350.60.5
114.7
0.470.470.330.37
Three episodes of aeolian construction have been identi�ed visually (Figure 2) and statistically [1] (Figure 3) in the 2016 ESA ExoMars lan-ding site (Figure 1) suggesting that Meridiani Planum had a complex history of erosion end deposition triggered by di�erent wind regi-mes (Figure 4) (see also [2]). The three bedform populations are:1) TAR population 1 (Figure 2a-c), located inside craters, consists of NE-SW trending bedforms lying stratigraphically on top of the TAR population 2. 2) TAR population 2 (Figure 2a-e) can be divided in two di�erent subclasses: 2a) large reticulate TARs (ladderback) [3,4,5] with three/two classes of crestlines (Figure 2c) with the main crestlines trending N-S (Figure 2b, Table 3b). The high directional variability characterizing trend measurements (Table 3b) suggests a strong topogra- phic control; 2b) smaller wavelength TARs (Table 3b) which can be found in continuity (Figure 2c and inset) or stratigraphically below the subpop. 2a (Figure 2d). This population is mainly located on the plain and has a similar trend to the subpop. 2a (Figure 2b). We also noticed two new important things: I) the occurrence of these bedforms is strongly topographically controlled as they clu- ster in the lee of impact craters forming a new type of wind streaks, the TAR-streaks (Figures 1, 2c inset, 2e). These streaks have an east to west direction suggesting they were formed by strong easterlies; II) the megaripples [6,7] are grouped in bands de�ning an older E-W orientation which we interpreted as a relict bedform pattern, the population 3 (Figure 2e-g).3) Bedform population 3 appears as an alternating bright/dark banding on HiRISE images (Figure 2e, f ). The paleo bedforms trend E-W (Figure 2b) and are locally in�uenced by the presence of depressions such as old eroded impact craters (Figure 2e). The paleobedform signature is locally erased by the TAR-streaks occurrence (Figure 2e). Y junction terminations are common (Figure 2f ) and DTM analysis shows that these features have a clear topographic expression (~1-1.5 meters high, Figure 2f, g).
FIGURE 2, BEDFORM PATTERN GROUPS FIGURE 3, BEDFORM PATTERN MEASUREMENTS
FIGURE 4, GEOMORPHIC BACKSTRIPPING
Di�erent generations of aeolian bedforms give rise to the observed complex pattern. Bedform pop. 4 might represents a relict linear or transverse (zibars?) dune pattern.Pops. 1 and 2 were likely emplaced by uni-directional winds. Bedform surface induration/cementation likely followed each constructional stage favouring the development of thecomplex pattern
ESA 2016 landing el-lipse in Meridiani Planum. HiRISE ima-gery and stereo deri-ved topography have beenused to study aeo-lian bedform mor-phology (background: nighti-me THEMIS IR mosaic)
A�liations: (1) INAF Osservatorio Astronomico di Capodimon-te - Napoli (Italy), (2) Centre for Geophysics University of Coim-bra (Portugal), (3) CERENA, Lisbon (Portugal), (4) INAF - Osser-vatorio Astronomico di Collurania - Teramo (Italy)
References: [1], Ewing et al. (2006), ESP&L; [2]Fenton et al. (this session); [3], Reddering (1987), Sedimentology; [4], Ramsay et al. (1989), Marine Geology; [5], Rubin et al. (2012), GSA meeting abst.; [6]Sullivan et al. (2005), Nature; [7], Golombek et al. (2010), JGR to be submitted...soon
a) TAR pops.1 & 2, b) circular distributions of the bedform crestline trend for the three pops. identi�ed c) TAR pops. 1 & 2 and location map (TAR streak - inset) d) locally the TAR subpop. a is found on top of subpop. 2b e-f-g) bedform pop. 3 which has a clear signature in the DTM rising 1-1.5 meters above the ground, g) 3D perspective of the orthoimage in panel f (10x v.e.)
a) cumulative log frequency plots of crest spacing and length [1], note the in�ection in the wavelength measurements marking the two subpopulations a and b (red line) b) main statistic parameters of the three populations identi�ed
FIGURE 1, STUDY AREA & METHOD
EVIDENCE FOR DIFFERENT EPISODES OF AEOLIAN COSNTRUCTION IN THE 2016 EXOMARS LANDING SITE IN MERIDIANI PLANUM (MARS)
(1) S. Silvestro, (2,3) D.A. Vaz, (4) G. Di Achille, (1) C. Popa and (1) F. Esposito([email protected])
