'Lucky' MESSENGER data upends long-held idea about Venus' atmosphere

What started as a dry run to ensure instruments on NASA's Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft worked properly later turned into a 10-year saga that resulted in a chance discovery unrelated to the mission's target planet, Mercury. It's about Venus and its atmosphere.

The team reports April 20 in Nature Astronomy that data fortuitously collected by MESSENGER reveals a sudden rise in nitrogen concentrations at about 30 miles above Venus' surface, demonstrating the planet's atmosphere isn't uniformly mixed, as expected. That finding upends an understanding about Venus' atmosphere that has prevailed for decades.

The story started in June 2007 as MESSENGER sailed above Venus for its second flyby before veering toward Mercury. Mission instrument teams took the opportunity to test their devices and collect data before the real show was set to begin some six months later.

Among the team members was David Lawrence, a nuclear physicist at APL. He was the instrument scientist for MESSENGER's neutron spectrometer, which detects neutrons set loose into space from cosmic rays colliding with molecules in a planet's atmosphere or surface. It aimed to find the telltale signs of neutrons coming from hydrogen atoms in water molecules that were suspected (and later confirmed) to be frozen in the crater shadows at Mercury's poles.

Over Venus, however, Lawrence just wanted to collect some data to verify the instrument was operating correctly. An initial check showed it worked, and the data was tabled.

But in 2010, Lawrence revisited those measurements, this time with Patrick Peplowski, another nuclear physicist at APL. Despite 50 years of sending robotic missions to Venus, including 13 atmospheric probes or landers, a lot of uncertainty about the nitrogen concentration in Venus' atmosphere, especially between 30 and 60 miles above the surface, remained.

Peplowski and Lawrence say this new result underscores the caution researchers need when drawing conclusions about atmospheric data, especially with the growing interest in planetary atmospheres in other solar systems.

...

Does this mean that we should be skeptical of consensus?

This article prompted me to find the account of the Russian probe that landed on Venus in 1970. I had forgotten about Venera 7. This is from wikipedia

“The parachute opened at a height of 60 km, and atmospheric testing began with results showing the atmosphere to be 97% carbon dioxide. The parachute was initially reefed down to 1.8 square meters, opening to 2.5 square meters 13 minutes later, when the reefing line melted as designed. Six minutes after the unreefing, the parachute started to fail, resulting in a descent more rapid than planned. The parachute eventually failed completely, and the probe entered a period of freefall. As a result, the lander struck the surface of Venus at about 16.5 m/s (37 mph)

The probe appeared to go silent on impact, but recording tapes kept rolling. A few weeks later, upon a review of the tapes by the radio astronomer Oleg Rzhiga, another 23 minutes of very weak signals were found on them. The spacecraft had landed on Venus, and probably bounced onto its side, leaving the medium gain antenna not aimed correctly for strong signal transmission to Earth.

The probe transmitted information to Earth for 53 minutes, which included about 20 minutes from the surface. It was found that the temperature at the surface of Venus was 475 °C (887 °F) ± 20 °C.”

It may be possible, within the next century or so, to start a “terraforming” of the atmosphere of Venus, by “seeding” it with several captured “dirty snowball” comets, steered to collide with the planet as it passes, and releasing airborne microorganisms to proceed with the transformation of the composition of the atmosphere, releasing the water to start its cycle of cooling the planet to a tolerable temperature range, and eventually forming oceans.

The real estate possibilities alone would be, like, opening up a whole new world.

Lawrence knew of a 1962 paper, however, that suggested neutron spectroscopy could help determine Venus' atmospheric nitrogen concentration. Nitrogen is fairly good at scavenging loose neutrons, unlike carbon and oxygen, which are some of the worst. So on Venus, the number of neutrons an instrument detects should depend on the amount of atmospheric nitrogen. Nitrogen concentration through Venus' atmosphere. New analysis of MESSENGER data shows an uptick in nitrogen concentration around Venus' upper cloud deck roughly 30 miles (50 kilometers) up, upending a long-held idea that nitrogen is distributed equally throughout. The red line is a trend line fitted to data from multiple missions, including MESSENGER's data, which was collected between 35 and 65 miles (60 and 100 km) high. Credit: Johns Hopkins APL... When they compared their models with the MESSENGER data, they found the best match was when atmospheric nitrogen made up 5% of the volume, about 1.5 times that measured lower in the atmosphere. And all of the neutrons came from a region between roughly 35 and 60 miles above the surface -- exactly where there had been the greatest uncertainty.

The Immanuel Velikovsky and Velikovsky keywords, sorted, duplicates out:

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