Could Venus’ atmospheric dark streaks be life? Mission proposes to find out

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A clever mission concept, proposed as a joint Russian/U.S. unmanned probe to Venus, would use a solar-powered unmanned aerial vehicle (UAV) to fly through the atmosphere for at least a year in order to try to find out the nature of the planet’s atmospheric mysterious dark streaks.

Descending hypersonically into the atmosphere after detaching from the orbiter, the UAV would be filled with hydrogen or helium gas, keeping it buoyant at a nominal floating altitude of 50 kilometers, allowing it to glide through the clouds while moving through the night-time hemisphere. Upon daylight, the solar-powered propellors would kick in and raise the craft’s altitude to around 60 kilometers.

Over the course of three to four days, the craft could move around the planet along the upper atmosphere’s ‘super-rotation,’ the strange phenomenon where the atmosphere seems to be uncoupled from the solid planet and rotates much faster. The UAV would therefore be able to explore the clouds at different altitudes, moving from air mass to air mass, from regions with UV absorbers to regions devoid of them, sampling and measuring the composition of the atmosphere.

The dark streaks, first photographed when Mariner 10 flew past on February 5, 1974 and took more than four thousand pictures, are made of a still unknown material in the upper clouds that absorbs ultraviolet light. The scientists of this mission concept propose that these dark streaks could even be Venusian life.

Finding life at high altitude in the atmosphere of a planet would make sense. After all, microbes have been found at similar heights in Earth’s atmosphere. The challenge for life on Venus is the planet’s extreme temperature. The surface, at 462º C (864º F), is hot enough to melt lead, and the surface pressure of 92 bar is the equivalent of being almost a kilometer under water.

However, in a region beginning around 50 kilometers in altitude and extending a dozen kilometers outward is a sweet spot where the temperature ranges between 30ºC and 70ºC (86ºF to 158ºF) and the pressure is similar to Earth’s surface. Life could potentially survive in this zone where the dark-streaking UV absorber is found.

Intriguingly, the sulfuric acid droplets within the clouds aren’t necessarily a show-stopper to life. Earlier Venera missions detected elongated particles in the lower cloud layer that are about a micron long, about the width of a small bacterium. These particles could be coated in ring-shaped polymers of eight sulphur atoms, called S8 molecules, which are known to exist in Venus’ clouds and which are impervious to the corrosive effects of sulfuric acid. Furthermore, S8 absorbs ultraviolet light, re-radiating it in visible wavelengths. If the particles are microbes, they could have coated themselves in S8, making them resistant to the corrosive effects of sulfuric acid. It has even been postulated that the S8 exists as a result of microbial activity.


  • LocalFluff

    Finding life on Venus would shock the space community. Venus is the nearest and most Earth like planet. It would look stupid to have missed the easiest and most obvious place to look by neglecting Venus. It was resurfaced only about 0.3 billion years ago. Whether it was a volcanic process or a major impact, its surface might’ve been very habitable during 4+ billion years before that. Its thick atmosphere might be a result of that resurfacing event. In only 0.01 or so billion years Mars’ moon Phobos with be crushed by tidal forces and rain down on Mars. Incredibly, after having been there for 4.55 billion years. Maybe Venus had a moon, a bit larger, in a similar situation, that crashed into it 0.3 billion years ago? The field is open for speculation since so little is known about Venus.

    The Discovery program picks the other day, turning down the two Venus alternatives, maybe opens up for a larger New Frontiers mission with proposed Venus orbiter and lander instead.

  • Orion314

    Always read / long ago/ that Mercury was the logical choice for the lost moon of Venus..

  • wayne

    “Venera-4” 1967 documentary

  • Alex

    LocalFluff: It is shame how less is done about Venus by NASA, despite its recognized huge scientific value in order to understand Earth’s and Solar system’s creation!!! There are so many good Venus mission proposals out there!

  • Max

    I’m very excited about this type of mission. A probe staying aloft in the atmosphere will give us the data we need to understand what elements were up against. Wind speeds, temperature, acid PH, to understand if we could survive a floating settlement.
    The temperature sounds comfortable at 50 kilometers from the surface (at one bar of pressure). Unfortunately, carbon dioxide clouds extend much higher. a solar panel will have to float above cloud cover at near 200° below zero. (The evaporation of carbon dioxide ice crystals?)
    The dark streaks, that might be life S8, appear float around the planet one revolution every two days indicating that there are extreme winds on Venus.
    I hope they use helium to keep the probe a loft. Nothing man-made can hold hydrogen for very long without being replenished. The hydrogen atom is four times lighter than helium but it also passes right through nearly all materials.

    Orion: If mercury was a moon of Venus, they would be orbiting each other like charon and Pluto. Even through mercury is smaller than two moons, Ganymede and titan, it is the second densest planet in our solar system. Gravity is 38% of earth. Some think it may have been the solid core to a gas giant that was destroyed near Jupiter making the astroid belt. Mars and Thea (Luna) may have been its moons before the destruction. I hope I live long enough for Space missions to drill Core samples to determine origin.

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