Between the late 2020s and early 2030s, NASA’s DAVINCI probe will take a look at Venus's atmosphere in unprecedented detail by dropping a probe with a spectrometer to the planet’s surface.
Image Credit: Dotted Yeti/Shutterstock.com
Despite being closer to Earth, Venus, the second planet from the sun, has been explored less than Mars. This is because, as inhospitable as the Red Planet is, the violent conditions of Venus — including temperatures that can melt lead — have so far precluded in-situ investigations.
This will change in the late 2020s when the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) launches from Earth and heads to Venus.
NASA, which is heading the mission, says DAVINCI¹ will study the origin, evolution and present state of Venus in unprecedented detail and will be the first mission to measure critical aspects of Venus’ massive atmosphere-climate system — a goal of planetary researchers since the 1980s.
As well as performing gravity-assisted flybys of Venus, DAVINCI will also drop a probe through the planet’s atmosphere. This will make DAVINCI the first mission to study Venus using spacecraft flybys and a descent probe.
One of the key tools that the craft will use to study Venus is spectroscopy — the study of the absorption and emission of light by chemical elements. Because each element absorbs and emits light in a characteristic and individual way, spectroscopy is an ideal method of analyzing chemical compositions and has been particularly successful in assessing the elemental make-up of stars.
In a paper² published in The Planetary Science Journal researchers laid out the strategy that DAVINCI will use to crack the mysteries of the second planet from the sun.
The DAVINCI Mission Flybys
Following its planned launch in 2029, and to make its flybys of Venus, the briefcase-sized DAVINCI craft will use gravity assists and its CRIS flight system to change speed and direction.
As it performs two flybys over Venusian clouds, DAVINCI — essentially a flying analytical chemistry laboratory — will examine the tops of these clouds in infrared and ultraviolet light. This will allow it to use spectroscopy to assess how they absorb ultraviolet light thus revealing their chemical composition.
These clouds sit on top of a thick, toxic atmosphere filled with carbon dioxide. They are yellowish in color and composed mostly of sulfuric acid. They serve to trap heat on the planet causing a runaway greenhouse effect that makes Venus the hottest planet in the solar system.
The first flyby will occur six and half months after launch and the two flybys will result in the craft collecting over 60 gigabits of new data about the atmosphere and surface of Venus.
Following these flybys, the craft will make a third sweep of the planet. The aim of this pass will be to position the DAVINCI craft in the ideal position to drop a probe into the atmosphere of Venus — allowing it to picture one of the planet’s mountain ranges Alpha Regio under ideal lighting at high noon.
The Descent to Venus
Occurring after two years of the mission, in 2031, DAVINCI will drop a probe into Venus’ atmosphere to a mountainous region called Alpha Regio studying its composition as it falls.
The spherical probe that DAVINCI will drop through the violent atmosphere of Venus is constructed of titanium — one of the strongest metals known — and is about 3 feet (1 meter) in diameter.
The five measurement instruments housed by the probe are also designed to survive these extreme conditions. This is no mean feat considering that temperatures on the planet can reach as high as 900 degrees Fahrenheit (475 degrees Celsius) — hot enough to melt lead.
This does not mean that the probe is indestructible, however, it has not been designed to survive its one-hour-long descent through the atmosphere of Venus, even with a parachute deployed to slow its fall — also increasing the amount of time it has to collect data.
During this descent, the probe will begin to interact with the atmosphere of Venus at around 75 miles (120 kilometers) above the surface. Its scientific measurements will begin at an altitude of 42 miles (67 kilometers) after it has abandoned its heat shield.
The probe will take thousands of measurements which will include ingesting atmospheric gases through its inlets for chemical analysis similar to those the Curiosity Rover is performing on Mars.
This allows gases from the Venusian atmosphere to be directly assessed using an instrument called the “Quadrupole Mass Spectrometer” (QMS), which NASA calls the “nose” of the instrument. QMS acts as a filter sorting each molecule and then “sniffing out” both isotopes of each element and their abundances.
For elements below the sensitivity limits of QMS — such as the noble gases Xenon and Krypton — the probe contains a chemical “scrubber” called the Gas Processing System (GPS). This can remove higher abundance elements and isotopes to leave the rarer elements to be collected in a cold trap. These are then sent to QMS for analysis.
The descent sphere also contains the Venus Tunable Laser Spectrometer (VTLS) and the Venus Atmospheric Structure Investigation (VASI).
Using another instrument —the Venus Descent Imager (VenDI) — as soon as the probe emerges from the thick Venusian clouds at around 100,000 feet, it will begin recording images of the rusty-colored volcano-strewn surface of Venus as it races towards it. This will be the first time any human probe has conducted descent-based surface imaging of Venus.
Though the probe is not expected to survive its 25-mile per hour (12 meters per second) touchdown on the surface of Venus, NASA researchers are preparing for the possibility that the hardy technology could be robust enough to do just this.
They estimate this will give the probe a maximum operation time of 17 to 18 minutes under the crushing atmospheric pressures, which are more than 90 times that of Earth and equivalent to those found a mile below the surface of the oceans of our planet.
In a NASA press release, Planetary Science Journal and DAVINCI principal investigator from NASA’s Goddard Space Flight Center, Jim Garvin, discussed the DAVINCI mission and the treasure trove of data it stands to deliver to researchers across a multitude of fields:
“This ensemble of chemistry, environmental, and descent imaging data will paint a picture of the layered Venus atmosphere and how it interacts with the surface in the mountains of Alpha Regio, which is twice the size of Texas,” said Garvin.
These measurements will allow us to evaluate historical aspects of the atmosphere as well as detect special rock types at the surface such as granites while also looking for tell-tale landscape features that could tell us about erosion or other formational processes.
Jim Garvin, Planetary Science Journal and DAVINCI principal investigator, NASA’s Goddard Space Flight Center
DAVINCI Probe's Eye View
Video Credit: NASA Goddard/YouTube.com
References and Further Reading
¹ DAVINCI Probe, NASA, https://ssed.gsfc.nasa.gov/davinci/mission
² Garvin. J. B., Getty. S. A., Arney. G. N., et al, , Revealing the Mysteries of Venus: The DAVINCI Mission, The Planetary Science Journal, https://iopscience.iop.org/article/10.3847/PSJ/ac63c2