What one spacecraft could not measure
In the peer-reviewed study published in Science Advances on 31 July 2026 the division of labour is explicit: MAVEN measured ions escaping near Mars while Tianwen-1 monitored the solar wind upstream. Lead author Chi Zhang says measuring the incoming wind and the escaping ions at once with a single spacecraft was a major challenge.[1]
This follows from measurement geometry, and its effect is large. An escape rate gathered by one spacecraft stays a number on its own: it says the planet is losing atmosphere and passes over what was driving the loss at that moment. With a second observer standing upstream, the same number can be matched to a driver. A plainer reading also remains available: part of the match could arise from the two craft seeing the same large-scale wind event from different positions, and separating that requires more events.[1]
The flux inside the cloud
According to the paper's abstract, the joint observations give direct evidence that the localized plasma clouds carrying ions are nonlinear wave packets generated by the Kelvin-Helmholtz instability. Two-point measurement constrains the spatial scale of those waves for the first time. The figure is given too: ion fluxes within plasma clouds are one to two orders of magnitude higher than those in typical steady-state escape channels.[1]
A flux difference reaching a hundredfold does not by itself fix this channel's weight in the loss budget, because the budget depends on how often and over how wide an area these clouds form as much as on the flux. The scale constraint matters here: once frequency can be measured, the total share becomes computable. That escape appears mainly on one side of the planet, and that the side depends on the direction of the solar wind's electric field, is a second observation supporting the mechanism. A random loss process would not pick a side.[1]
The next measurement
The observation that will really test this result is straightforward: when the direction of the electric field turns, the side where escape concentrates should turn with it. That is expected in every period when the two craft are again suitably placed at the same time, and if the predicted reversal does not appear, the mechanism's share of the escape budget drops. The team itself calls for additional spacecraft observations and numerical simulations; if results from the next observing series are published by the middle of 2027, the figure will rest on more than a single event for the first time.[1]