Category Archives: Mercury and Venus

Videos: Solar observatory spacecraft captures great views of Mercury transit

The Mercury transit was seen by observers on the ground and by satellites in space. The best views of the transit came from the Solar Dynamics Observatory (SDO) spacecraft, whose multiple imagers showed the transit in different parts of the spectrum:

Another SDO view:

Here is a NASA panel discussion about the transit:

Mercury to transit the Sun on Monday

On Monday the planet Mercury will transit across the face of the Sun as seen from earth between about 7:12 am  and 2:42 pm EDT : Mercury Enters Spotlight on May 9 – NASA.

This video shows the path that it will take:

Don’t ever look directly at the sun. There are various safe ways to observe the transit such as using a solar filter over a telescope aperature or to project the image onto a white board with a pinhole. The transit will also be webcast from various sites.

Here are some sites with information on webcasts and tips on viewing the transit directly:

Exploring Venus with an air ship

Over the years there have been those who have argued that Venus, not Mars, is the best place for humans to explore and even settle. They are not proposing that people go down into the poisonous atmosphere and onto the hellishly hot surface but instead to use habitats that float upon the dense atmosphere. The proverbial cloud cities of innumerable science fiction books and movies could eventually become feasible. Last summer I posted some links to such proposals: Colonies on the clouds of Venus.

A NASA group has released a study outlining an exploration program of Venus that is based on airships: NASA Study Proposes Airships, Cloud Cities for Venus Exploration: Should crewed exploration of Venus come before we try to go to Mars? – IEEE Spectrum.

This video shows the architecture of such an exploration program:

NASA Langley researchers want to get a better idea about conditions on our nearest planetary neighbor, Venus, so they have come up with HAVOC or a High Altitude Venus Operational Concept – a lighter-than-air rocket ship that would help send two astronauts on a 30-day mission to explore the planet’s atmosphere. Exploration of Venus is a challenge not only because its smog-like sulfuric acid-laced atmosphere, but also its extremely hot surface temperature and extremely high air pressure on the surface.

Colonies on the clouds of Venus

Living atop the clouds of Venus might be feasible and offer some advantages over the surface of Mars:

Venus Express sees a glory

A post by ESA about a recent observation from the Venus Express orbiter:

Venus glory 

A rainbow-like feature known as a ‘glory’ has been seen by ESA’s Venus Express orbiter in the atmosphere of our nearest neighbour – the first time one has been fully imaged on another planet.

Rainbows and glories occur when sunlight shines on cloud droplets – water particles in the case of Earth. While rainbows arch across wide swathes of the sky, glories are typically much smaller and comprise a series of coloured concentric rings centred on a bright core.

False colour composite of a ‘glory’ seen on Venus on 24 July 2011. The
image is composed of three images at ultraviolet, visible, and near-infrared
wavelengths from the Venus Monitoring Camera. The images were taken
10 seconds apart and, due to the motion of the spacecraft, do not overlap
perfectly. The glory is 1200 km across, as seen from the
spacecraft, 6000 km away.

Glories are only seen when the observer is situated directly between the Sun and the cloud particles that are reflecting sunlight. On Earth, they are often seen from aeroplanes, surrounding the shadow of the aircraft on the clouds below, or around the shadow of climbers atop misty mountain peaks.

A glory requires two characteristics: the cloud particles are spherical, and therefore most likely liquid droplets, and they are all of a similar size.

Venus glory details
Three images showing the glory at ultraviolet (left,) visible (centre) and
near-infrared (right) wavelengths as taken by the Venus Monitoring Camera.
The feature was observed on 24 July 2011 and measures 1200 km
across, as seen from the spacecraft, 6000 km away

The atmosphere of Venus is thought to contain droplets rich in sulphuric acid. By imaging the clouds with the Sun directly behind the Venus Express spacecraft, scientists hoped to spot a glory in order to determine important characteristics of the cloud droplets.

They were successful. The glory in the images here was seen at the Venus cloud tops, 70 km above the planet’s surface, on 24 July 2011. It is 1200 km wide as seen from the spacecraft, 6000 km away.

From these observations, the cloud particles are estimated to be 1.2 micrometres across, roughly a fiftieth of the width of a human hair.

The fact that the glory is 1200 km wide means that the particles at the cloud tops are uniform on this scale at least.

The variations of brightness of the rings of the observed glory is different than that expected from clouds of only sulphuric acid mixed with water, suggesting that other chemistry may be at play.

One idea is that the cause is the “UV-absorber”, an unknown atmospheric component responsible for mysterious dark markings seen in the cloud tops of Venus at ultraviolet wavelengths. More investigation is needed to draw a firm conclusion.