It is time to ship a lander to Mercury

So much of the astronomy community revolves around the decadal poll. Teams of dozens of scientists have spent hundreds of hours developing proposals that will eventually seek to influence the polls’ recommendations, which will affect billions of dollars in research funding over the next decade. And now is the best time to submit these proposals. One of the most ambitious is sponsored by a team led by researchers from the Applied Physics Laboratory (APL) at John Hopkins University. Your suggestion – it’s time to land on Mercury.

This isn’t the first time the idea has aired, but new technology is making this incarnation feasible for the next decade. The current proposal was first forwarded to NASA by APL scientists, which funded a mission concept study that produced an in-depth 82-page review of a mission draft available from NASA.

Detailed discussion of the mission concept by Dr. serious
Credit – The Lunar and Planetary Institute YouTube Channel

There are five main mission objectives:

  1. Land safely and collect data on Mercury’s surface
  2. Learn more about the mineralogy and chemistry of Mercury
  3. Study the magnetic field and internal structure of the planet
  4. Understand the processes affecting Mercury’s regolith and exosphere
  5. View the surface up close to determine the ground truth to calibrate the object size for orbital measurements

Every lander faces a daunting challenge when landing. Currently, the best images we have of the innermost planet were captured by NASA’s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015. However, these images only cover minimal portions of the surface and their resolution is not ideal for choosing a particular landing site. Each pixel in the high-resolution images that MESSENGER returned covered, at best, 2–3 m of the planet’s surface.

Graphic of the lander included in the report showing potential scientific payloads, engineering requirements, and orbital mechanics.
Credit – Ernst et al.

This resolution is not good enough if a 3 meter boulder could completely overturn the lander on its descent. BepiColombo, an ESA / JAXA mission currently en route to Mercury, should be able to capture some higher resolution images that could aid in landing. However, the process will most likely still rely on an autonomous landing protocol.

Assuming the lander lands, it has to get to work quickly. The mission should only last during Mercury’s night, which is 88 Earth days long. Trying to construct a lander to withstand the full force of the sun during Mercury day would require too many of the instruments the lander hopes to carry. In its current iteration, the mission would plan to touch down on the planet during dusk and then operate continuously for about three months before the mission ends at dawn.

Mission objective timeline with the 88 day time limit on earth.
Credit – Ernst et al.

However, a lot of scientific work can be done during these months. During twilight, the lander will take some panoramic shots of its surroundings to provide context for the smallest rocky planet for the first time. It will also be equipped with lights that will allow it to illuminate its immediate surroundings even in the pitch black night of Mercury.

This light and all instruments on board are fed by a radioisotope thermogenerator, a common power supply for space lander and rovers. Its adoption reveals another important aspect of the lander’s mission design – it will use technologies that have already been developed.

UT video discussing some of Mercury’s interesting features.

The techniques required to achieve the mission’s scientific objectives are similar to those already used on other planets. Many of the technologies, such as magnetometers and spectrometers, can be reused from designs used on other missions. This would reduce the overall cost of the mission, which would not have to do the development work for its scientific instruments from scratch.

That scientific instrumentation would still be pretty impressive. The proposed suite of instruments includes several spectrometers, cameras, and magnetic sensors, all of which should work on Mercury Night. However, the mission designers emphasize that the exact payload is still flexible, in the expectation that other technologies will be adapted as needed in future mission planning.

Go over, Pluto … Disney already has Mercury, as shown in this MESSENGER photo.
Photo credit: NASA / JHAPL / Carnegie Institution of Washington

Dr. Carolyn Ernst, PI of the Mission Concept, is excited to see what these proven instruments will discover. “Mercury is the only rocky planet we haven’t landed on – we’ve never seen the surface up close. We need land measurements to better understand Mercury and put our own earth in context, ”she says.

But comparing Mercury to Earth isn’t the only reason to go there. Dr. Nancy Chabot, the Deputy PI of the Mission Concept, points out that the data collected so far about Mercury are limited and difficult to interpret. To put it in their words, “It’s exciting to fill this black box,” where the “black box” refers to an illustration in the report that shows an image of the surface of each of the rocky worlds in the inner solar system, but Mercury is only referred to as Black box, because such a view does not yet exist.

Mercury is literally a black box as we don’t yet know what its surface looks like.
Credit – Ernst et al.

Drs. Ernst and Chabot and their colleagues have been puzzling over the mysteries of Mercury for years, as they were significantly involved in the planning and analysis of the data from the MESSENGER mission. But they see this successful mission only as a first step in truly understanding this unique planet.

There is still much work to be done before any country will contribute to this understanding. The final report of the Decadal survey, which may suggest prioritizing the mission, will be available in a little less than a year. The APL team is busy working out mission plans and ideas to make the idea of ​​a Mercury lander as attractive as possible. Still, the Mercury researchers will hopefully have more to cheer when BepiColombo is about to arrive on the innermost planet in 2025. The success of this mission could spark more interest in Mercury itself – possibly in a data-rich land, and finally, some images of the surface to fill Mercury’s blank space in our solar system’s scrapbook.

Learn more:
APL – Merkurlander – What does it take to land on Mercury? It’s time to find out, say scientists
NASA – Mercury Lander Mission Concept Study
UT – missions to Mercury

Mission statement:
Artistic concept of a lander on Mercury.

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