A Jupiter-bound probe flew through a CME that Earth-side forecasters had written off

A plasma instrument on NASA's Jupiter-bound Europa Clipper flew through part of a coronal mass ejection on December 19, 2024 that forecasters working from Earth's viewpoint had expected to miss the planet entirely ^[1][8][11]. The miss was a matter of viewing geometry rather than instrument failure, which means the space-weather forecasts that satellite and grid operators plan around carry a structural blind spot that no amount of Earth-facing observation closes ^[10][20].

The detection was an accident of scheduling. Europa Clipper, launched about two months earlier from Kennedy Space Center and on its way to conduct the first detailed study of Jupiter's moon Europa, was running a routine checkout of its Plasma Instrument for Magnetic Sounding, or PIMS, an instrument built to measure the density, temperature and flow of plasma near Europa ^[1][3][21]. PIMS recorded fast solar wind carrying plasma hotter and less dense than usual ^[2]. Adrienn Luspay-Kuti, the instrument's principal investigator, told Gizmodo that the team's first job was to establish that the signal came from the space environment and not from an artifact of the instrument or spacecraft ^[4]. Gizmodo reports the probe was then more than 17 million miles from the Sun, heading toward Mars and roughly in line with Earth, and that the plasma properties were atypical for solar wind at that distance but typical of structures produced by coronal mass ejections ^[18][19].

Working backward, the team tied the signal to a large filament eruption a few days earlier that produced a CME, then reconstructed the event using observations from 17 spacecraft across the inner solar system ^[6][5]. The reconstruction, published in Science Advances, found a structure that did not expand evenly outward like a bubble but developed a very irregular shape ^[5][7]. Seen from Earth, the main body appeared to be heading south and away, so forecasters expected no impact ^[8]. NASA's STEREO-A, viewing the eruption from the side, saw a second component moving toward Earth that was invisible from Earth's line of sight, and that component is what PIMS flew through ^[9][11]. The paper's conclusion is blunt about the dependency: the Earth-directed piece could not have been predicted without spacecraft positioned off the direct Sun-Earth line ^[10].

That matters because the failure mode is a false negative on the exact class of event operators buy protection against. CMEs aimed at Earth can trigger geomagnetic storms that disrupt power grids, scramble satellite communications, cause radio blackouts and expose astronauts in orbit to radiation ^[15]. The same component reached Mars, where NASA's MAVEN orbiter detected it ^[12]. No damage to Europa Clipper or MAVEN is reported ^[14]. Luspay-Kuti's framing is about crew: Europa Clipper was crossing the region between Earth and Mars where astronauts may someday travel, and the largest hazard there is a sudden jump in radiation, because fast CMEs drive shocks that accelerate charged particles to very high energies ^[16][17].

Three things to watch. Whether this is a recurring pattern or a single documented case, since one event with no reported damage supports no failure rate ^[22]. Whether planetary-mission plasma data start being treated as operational forecasting input rather than a science byproduct ^[5][10]. And how the off-axis coverage holds up, given that MAVEN's observations of Mars ran only through late 2025 ^[13].