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Surficial Deposits Surficial Deposits and Access to Materials with and Access to Materials with Known Geological Context Known Geological Context

on Venus on Venus Mikhail KreslavskyMikhail Kreslavsky

University of California – Santa Cruz

In collaboration with: Nataliya Bondarenko Nataliya Bondarenko James HeadJames Head

GEOLOGICAL / GEOCHEMICAL DOMAINS OF VENUSafter Basilevsky and Head [today]

1. Whole Planet Emphasis on planet interior

2. Planetary Crust: Geologic bodies units seen in the radar images 100s m – 10s km thick

3. Planetary Surface layer: eolian and “impact” sediments seen in the panoramas and implied from microwave properties 10s mm – 10s m thick

4. Surface: Dust, Condensates, Weathering products millimeters to microns thick

This is what we wantto probe

And th

is is

what

we can

reac

h

Domain 4 - Surface

• Venus is a dusty planet ⇐ thick dry atmosphereFine dust:– is lifted by impacts– is suspended in the atmosphere– is distributed by high-latitude winds– slowly settles at the surface– sticks to rocks– is sintered and become a part of rocks

⇓spectroscopy does not probe local material

Domain 3 – Surficial deposits

• Surficial deposits seen in the radar images:impact-related diffuse features = meters-thick mantles

• splotches• dark crater halos• dark parabolas• etc

– Wind streaks• a great variety

– Dune fields • resolved dunes• microdunes


• Surficial deposits NOT seen in the radar images:– from Magellan radiometry:

• parabolas in emissivity are wider than in radar images

• emissivity-only parabolas

– from Magellan SAR –E-W backscatering anisotropy

– from Magellan radar altimeter N-S backscatering anisotropy

• ubiquity of eolian deposits

Bondarenko and Head, 2004


• Surficial deposits NOT seen in the radar images:– from Magellan radiometry– from Magellan SAR – E-W backscattering anisotropy– from Magellan altimeter - N-S backscattering anisotropy

Weitz et al. 1994



ubiquity of eolian deposits

Kreslavsky & Vdovichenko, 1999


Bondarenko et al., 2006






Bondarenko et al., 2006



⇓Surface is covered with decimeters or meters of non-local material almost everywhere.

Direct inference from SAR images Reality



⇓Surface is covered with decimeters or meters of non-local material almost everywhere.

Drilling is needed to access local materialor

Radar-dark parabolas give easy access to non-local material from known source

or

Search for gaps in the surficial deposits

Radiometry Radar

Conclusions• Mixed (indurated) dust from ambiguous remote sources

cover local materials everywherespectroscopy does not probe local material

• Surficial deposits are almost everywhere reliable access to igneous material requires ~10 m drilling capabilityCrater-related parabolas give reliable easy access to material from a known source

• There are limited areas with local igneous material within ~ 1 cm from the surface

they can be found by analysis of Magellan data