An innovative proposal would be a first for planetary exploration.<\/em><\/p>\n Turns out, it\u2019s as tough to drop inward into the inner solar system, as it is to head outward. The problem stems from losing momentum from a launch starting point on Earth. It can take missions several years and planetary flybys before capture and arrival in orbit around Mercury or Venus.<\/p>\n Now, a new proposal would see a mission make the trip, using innovative and fuel efficient means.<\/p>\n The new proposal comes out of the Advanced Concepts Office at the Marshal Space Flight Center, and was presented at the 56th<\/sup> Lunar & Planetary Science Conference (LPSC) held at the Woodlands, Texas in early March 2025. Mercury Scout would be a Discovery-class mission.<\/p>\n The spacecraft would utilize a traditional launch carrier plus a kick stage booster to get it off the Earth and into a solar heliocentric orbit. The innovative part of the mission, however, is the large solar sail it would unfurl once it’s in space. This would be the spacecraft\u2019s sole means of maneuvering and propulsion to reach and operate around Mercury.<\/p>\n<\/p><\/div>\n The mission has two stated main goals. The first is to map the surface to a meter scale to identify mineral resources and understand the geology and evolution of the planet. The second is to take advantage of a decade-long nominal mission to try and observe and understand geological processes still underway on the surface and in the interior of Mercury.<\/p>\n Instruments called for on the mission include a mid-infrared spectrometer for mineral mapping, a radiometer to measure surface temperature, and a Narrow Angle Camera (NAC) capable of 1-meter scale resolution.<\/p>\n A diagram series for the proposed Mercury Scout mission. Credit: JPL\/Caltech\/Brown University\/NASA MSFC<\/em><\/p>\n The small spacecraft will have an expected mass of 250 to 300 kilograms, about the mass of a large motorcycle. Mercury Scout would also employ a sun shade for protection versus the fierce solar intensity near Mercury. The mission would take advantage of NASA\u2019s Advanced Solar Sail Concept.<\/p>\n The mission uses for the Sun for two purposes: propulsion and power. To this end, the Mercury Scout will employ four reaction wheels to literally tack and roll with the solar wind.<\/p>\n Mercury Scout will employ four booms to deploy a 50002<\/sup> meter square sail after kick-stage jettison. The original mission called for a 25002<\/sup> sail (slightly larger than the one planned for Solar Cruiser at 17002<\/sup>). A larger sail allows for a 7-year transit time to Mercury, with no gravitational assists via planetary flybys. A larger 10000 (kilometer square) sail could allow for a transit time of less than 4 years.<\/p>\n Of course, adding a solar sail also adds complexity to any mission: if it fails to deploy, the entire mission is a loss. This was recently the case with NEA Scout, launched with Artemis 1. On the plus side, a purely solar-powered and propelled mission could perform a longer stay at Mercury, as it wouldn\u2019t have to carry propellant for reaction thrusters.<\/p>\n \u201cTaking advantage of the longevity of the solar sail propulsion, the orbital mission is broken into three phases,\u201d researchers state in the study proposal. \u201cEach phase…has (a) sun-synchronous and highly elliptical orbit.\u201d This would see the mission going from an elliptical to more circular orbit over a six year span, though mission planners hope for a decade of science and observations around Mercury.<\/p>\n Solar sailing sounds easy in theory, but is turning out to be tougher to pull off in practice. NanoSail D2, the Planetary Society\u2019s LightSail 2 and the recent ACS3 mission demonstrated that such a deployment and utilization of a solar sail in space is possible. In addition to propulsion, solar sails could also one day be featured as standard equipment on satellites, to deploy and create a higher drag to speed up reentry at the end of mission life. A mission named Breakthrough Starshot also could one day employ a sail and a powerful Earth or space-based laser to journey to Alpha Centauri.<\/p>\n Mercury is definitely in need of exploration. NASA\u2019s Mariner 10 performed the first flyby of the innermost world in 1974, revealing a planet with a decidedly Moon-like surface. To date, only NASA\u2019s MESSENGER mission has entered orbit around Mercury, exploring the world from 2011 to 2015. Late next year, the joint JAXA\/ESA BepiColombo mission will enter orbit around Mercury, as part of its 18 month nominal mission.<\/p>\n Tacking the winds that ply the solar system may yet have its day, and we may soon be solar-sailing to Mercury.<\/p>\n<\/p><\/div>\n![](\"https:\/\/www.universetoday.com\/assets\/sials.jpg\"\/)
Deployment testing for the solar sail used on the ill-fated NEA Scout asteroid mission. Credit: NASA<\/em><\/p>\n![](\"https:\/\/www.universetoday.com\/assets\/sail.jpg\"\/)
The aluminum-coated, thin-film polyimide used to make solar sails. Credit: NASA<\/em> <\/p>\n![](\"https:\/\/www.universetoday.com\/assets\/screenshot-2025-03-31-134608.jpg\"\/)
How a solar sail operates. Credit: Science at NASA<\/em><\/p>\n![](\"https:\/\/www.universetoday.com\/assets\/mercury-messenger_print.jpg\"\/)
Mercury, as seen from NASA’s MESSENGER mission. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington<\/em><\/p>\n