Dava Sobel - The Planets

Yes, the faces in the crowd,

And the wakened echoes, glancing

From the mountain, rocky browed,

And the lights in water dancing –

Each my wandering sense entrancing,

Tells me back my thoughts aloud,

All the joys of Truth enhancing

Crushing all that makes me proud.

James Clerk Maxwell,

‘Reflex Musings: Reflections from Various Surfaces’ *

Magellan’s radar images look like night-time aerial reconnaissance photos, except that instead of providing a visual record, their blacks and whites reflect the varying textures of Venus’s exposed beauty: hundreds of thousands of small Venusian volcanoes pop out as bright (rough) bumps against the dark (smooth) background of the plains. On the flanks of giant volcanoes, bright (new) layers of lava drape themselves over the dark (old) flows. Mountainsides glittering in radar brightness seem to boast slopes coated with a veneer of reflective metal, perhaps fool’s gold, that adheres to Venusian rock at the cooler temperatures a few thousand feet up.

Etched in these images, Venus reveals her unique oddities, such as overlapping ‘pancake dome’ volcanoes that rise from surprisingly round bases to flat or softly mounded tops, and her numerous ‘coronae’, or sets of concentric rings that ornately surround so many of her domes, depressions and crowds of small volcanoes. Rushing streams of lava dug the long riverine channels that wind across her ample plains. On her high plateaux, tectonic folding and faulting have decorated several thousand square miles to look like crazy-tiled floors, now called ‘tesserae’. Evocative patterns in Venus’s extruded lava and cracked ground that reminded scientists of sea anemones and spider webs have become ‘anemone volcanoes’ and ‘arachnoids’.

After amassing their gallery of radar portraits, Venus specialists enhanced many of the images with colour for improved resolution. They chose a fire-and-brimstone palette, beginning with the russet hue of the first photos taken by the Russian Venera spacecraft, continuing the theme in ochre, umber, sienna, copper, pumpkin and gold. The vibrant colours suit the seared scenery, the rock that spewed forth as lava and still retains its near-plastic consistency, the massifs ascending to altitude without ever hardening harder than toffee. Bright shades befit the youthful visage of a planet that only recently (within the last half billion years) repaved itself in veritable floods of lava, which welled up and covered over almost every vestige (about 85 per cent) of her ancient past.

Relatively few craters mar the new face of Venus, since the rate of cratering over these past 500,000 years is much reduced from the Solar System’s earliest days. Many small would-be intruders are vaporized on their way through the thick atmosphere, never to touch down, so that only the very largest impactors reach the surface intact. These collisions eject copious debris, yet all the rubble hugs close around the crater margins in neat festoons, as though contained there by the heavy air. The atmosphere likewise may have soothed the fury of Venusian volcanoes, compelling their expelled lava to seep and pour rather than erupt with explosive force.

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