Four billion years ago, Mars’ fate was sealed deep within its core. When the planet’s once-vigorous magnetic dynamo sputtered out, the invisible shield that had protected its thick atmosphere from the Sun’s charged particles, the solar wind-collapsed. Without that barrier, the atmosphere was gradually stripped away, and the planet’s rivers, lakes, and possibly oceans vanished into space. Now, NASA’s $80 million ESCAPADE mission is preparing to investigate that atmospheric escape in unprecedented detail, using two identical satellites to capture a three-dimensional, time-resolved view of the process in action.
Slated to lift off no sooner than Nov. 9 aboard the Blue Origin New Glenn rocket, the Escape and Plasma Acceleration and Dynamics Explorers, nicknamed Blue and Gold, will become NASA’s first dual-spacecraft mission to another planet. Each probe, about the size of a copy machine, carries a coordinated suite of instruments: UC Berkeley-built electrostatic analyzers to measure the direction and energy of escaping ions and electrons, a NASA Goddard magnetometer to map magnetic field strength and orientation, plasma sensors from Embry-Riddle Aeronautical University to characterize charged particle populations, and a student-built camera from Northern Arizona University to image Mars and its elusive green auroras.
The stereo vantage points of the mission will overcome a major limitation of past orbiters such as MAVEN and Mars Global Surveyor, which could sample only one location at a time. Flying in formation just minutes apart, the probes will monitor changes in Mars’ patchy crustal magnetic fields and ionosphere on timescales as short as two minutes. This will allow us to really make measurements we’ve never made before, and to characterise a very dynamic system in a way we couldn’t characterise it before, said principal investigator Robert Lillis of UC Berkeley’s Space Sciences Laboratory.
That dynamic system is shaped by the physics of solar wind–planet interactions. Mars lacks a global magnetosphere, but localised crustal fields can deflect the solar wind up to 1,500 kilometres above the surface. Hybrid plasma simulations and MAVEN observations show that under certain conditions, such as when the interplanetary magnetic field is nearly parallel to the solar wind flow, Mars can develop a degenerate, induced magnetosphere, allowing the solar wind to penetrate unusually deep into the ionosphere. This enhances ion escape, with heavy ions like O₂⁺ forming vast plumes extending tens of planetary radii downstream. ESCAPADE’s instruments are designed to capture such events in real time, measuring the electric fields, both convective and ambipolar, that accelerate particles away from the planet.
The mission will also investigate the long-standing mystery of Mars’ magnetic collapse: recent laboratory experiments that mimic a core made of iron, sulfur, and hydrogen imply that immiscible liquid layers may have stratified the Martian core, halting convection and shutting down the dynamo. Paleomagnetic analyses of meteorites suggest that the field may have endured until around 3.9 billion years ago, potentially extending habitable conditions. By quantifying today’s atmospheric loss rates and their drivers, ESCAPADE will help constrain models of how fast Mars shifted from a wetter, warmer world to the arid one we see today.
The flight to Mars will take a new trajectory. Rather than the conventional Hohmann transfer, which allows only a narrow launch window every 26 months, ESCAPADE will cruise first to a Sun–Earth Lagrange point, will loiter there for about a year, then slingshot past Earth toward Mars in 2026. This “queueing” approach could be critical for future human missions, when dozens of spacecraft may need to depart over extended periods rather than in a single launch window.
Once in Mars orbit in 2027, the probes will spend seven months adjusting into a “pearls on a string” formation about 160 kilometres above the surface. Following six months of tandem measurements, they will split into different orbits for five more months to map the three-dimensional flow of energy and matter between the solar wind and Mars’ atmosphere. Beyond pure science, the data have practical implications, too. The ionosphere can refract and reflect radio waves, a critical factor for communication and navigation by future astronauts. Understanding its variability will be key to designing robust systems. ESCAPADE’s measurements of space weather will also feed into radiation hazard forecasts. During one 2024 solar storm, NASA’s Curiosity rover recorded a single-day radiation dose equivalent to 100 days of background galactic cosmic rays. Integrating state-of-the-art plasma physics, novel orbital mechanics, and economical spacecraft design, ESCAPADE will shed light on the ancient past of Mars and the challenges of its human future.
