Mercury Will Stay a Puzzle Until a Lander Is Sent, Scientists Say

Mercury remains the least explored planet in the inner solar system, and the only new data will come from ESA/JAXA's BepiColombo, which enters orbit late next month but won't begin science operations until April 2027. Planetary scientists Paul Byrne and Anne Pommier argue that without a lander, key mysteries will persist: the iron-rich core making up about 85% of the planet's radius, its weak magnetic field and dark graphite-rich surface material.

• BepiColombo enters Mercury orbit late next month; science starts April 2027
• Iron-rich core is thought to make up about 85% of the planet's radius
• Mercury's magnetic field is roughly 100 times weaker than Earth's
• No further Mercury missions are on the drawing board after BepiColombo