The planet Mercury is the closest planet to the Sun, and the most difficult for spacecraft to visit and explore. This is because as the spacecraft approaches Mercury, the Sun’s gravity pulls on the spacecraft, greatly increasing its speed and making it difficult to decelerate without a lot of fuel. But what if a spacecraft could go and explore Mercury without fuel? This can significantly reduce mission costs while providing impactful science.
Now, a team of researchers from Brown University may be one step closer to making this mission a reality, as they propose a Discovery-class solar powered mission concept called Mercury Scout, which they presented in a study recently presented at the 57th Lunar and Planetary Science Conference. A Discovery-level mission is a low-cost NASA mission (less than $1 billion) designed for rapid development compared to larger, multibillion-dollar Flagship missions. For context and Mercury, NASA’s MESSENGER mission, which became the first mission to orbit Mercury, was a Discovery-class mission. For the study, the researchers discussed Mercury Scout’s performance, science goals, science tools, spacecraft design, and communication, and propulsion.
Arguably the most impressive feature of the Mercury Scout is its solar-sail propulsion, which uses sunlight to power the spacecraft. Along with not needing fuel, the researchers note that this method can also be used to control the trajectory and control of the spacecraft. In addition, with the reduced number of components and the smaller size of the spacecraft, researchers realize that the deployment of solar sails can extend the life of the spacecraft, adding a large collection of scientific data about the planet near the Sun. So far, the only spacecraft that has successfully used solar energy in space is Japan’s IKAROS project in 2010 and The Planetary Society LightSail-2 which successfully used solar sails to raise its orbit in 2019. NASA recently tested its Advanced Composite Solar Sail System (ACS3) technology, which was successfully launched in August 202 2024. While ACS3 is in low Earth orbit, the spacecraft, carrying a CubeSat roughly the size of a microwave oven, experienced a meltdown, which continues to be monitored.
The general purpose of Mercury Scout will be to perform geological imaging with a narrow angle camera (NAC), which provides high resolution images of up to 1 meter (3.2 feet) per pixel. For context, NASA’s Lunar Reconnaissance Orbiter uses a NAC with a resolution of 0.5 meters (1.6 feet) per pixel, and NASA’s MESSENGER spacecraft had a NAC capable of imaging resolutions up to 20 meters (65 feet) per pixel.
Using NAC, Mercury Scout’s scientific goals will be to understand Mercury’s history, as Mercury’s surface is estimated to be 26 kilometers (16 miles) thicker than the other planets in the solar system. Other science goals include examining current or recent geological events and comparing these findings to previous missions such as MESSENGER.
Given that Mercury Scout will focus on imaging, the NAC is intended to be the only science award. For temperature control, given its close proximity to the Sun, Mercury Scout will perform a long elliptical orbit from within about 200 kilometers (124 miles) to about 10,000 kilometers (6,214 miles) from Mercury’s surface. For communications, Mercury Scout will include a flat antenna like NASA’s MESSENGER and the Akatsuki missions of the Japan Aerospace Exploration Agency (JAXA), the latter of which was tasked with studying the atmosphere of Venus until the probe failed to enter orbit and was lost.
The study states, “This updated Mercury Scout concept demonstrates that a simplified, NAC-only payload combined with solar-sail propulsion can enable a focused, high-impact study of Mercury’s energy evolution by taking long-duration, high-resolution, meter-scale images from Mercury orbit using propellant-free structures.”
How will Mercury Scout help scientists explore Mercury in the coming years and decades? Only time will tell, and that’s why we’re science!
As always, keep up the science and stay tuned!
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