Three potential missions from the European Space Agency (ESA) are vying for funding, and scientists are about to discuss the benefits of each.

The missions are called ARIEL, THOR, and XIPE, and are designed to study exoplanets, space plasma physics, and X-ray emissions respectively. ESA is going to pick which one of the three missions to pick in November this year, with launch scheduled for 2025.

They were announced as candidates for ESA’s medium-class science missions back in June 2015, and they will now be presented to the scientific community at an event in Paris on July 3, 2017. All three have now completed their Assessment Phase, but only one will go forward into the Definition Phase.

Each mission has its selling points. Perhaps the most topical is ARIEL (Atmospheric Remote-Sensing Infrared Exoplanet Large-survey), which would study the atmospheres of 500 exoplanets around nearby stars.

A lot of thought is going into how to study atmospheres at the moment. This may be one of our best ways to find signs of life outside the Solar System, and this mission would determine the chemical composition and physical conditions of many useful atmospheres. This mission would focus on worlds in close orbits around stars, so potentially ones not habitable to life, but it would help give an insight into how planets form.

THOR (Turbulence Heating ObserveR), meanwhile, would try to work out how plasma is heated in the cosmos. The mission would orbit Earth, and would observe the interaction of the solar wind with Earth’s magnetic field.

Last but by no means least is XIPE (X-ray Imaging Polarimetry Explorer), which would study X-ray emissions from things like supernovae, galaxy jets, and black holes. The goal would be to work out how matter behaves in these extreme conditions.

ESA has three medium-class missions coming up that have already been picked. The Solar Orbiter will launch in 2018 to study the “surface” of the Sun. Euclid will launch in 2020 and attempt to map dark matter and dark energy. And Plato in 2024 will be looking for habitable rocky planets around Sun-like stars.

All the new proposals would be worthwhile, but sadly only one can be picked. We’ll have to wait and see which one makes the cut.