Scientific Rationale

Dynamically New Comets (DNCs) are the most preserved bodies in the Solar System and provide the unique opportunity to investigate the unaltered pristine materials from which the Solar System formed. DNCs have been found to be already active at about 26 AU from the Sun where the temperature is too cold to allow water ice to sublimate. At those distances, the sublimation of supervolatile ices like CO2 and CO is considered responsible for activity.

However, little is known on how specifically the activity pattern switches from being driven by supervolatiles to being driven primarily by water. The recently selected ESA mission Comet Interceptor will encounter a Dynamically New Comet (DNC) that will be discovered and selected at about 8-10 AU from the Sun, in its inbound orbit. Comet Interceptor will approach its target around perihelion, at about 1-1.5 AU.

Our capacity to anticipate the target behavior and activity levels at the encounter will definitely influence the target selection and therefore the scientific return as well as the safety of the mission itself.

Our ISSI International Team to investigate and characterize the transition from the supervolatiles-driven activity and the water-driven activity.

The Team will be using a multidisciplinary approach taking advantage of

1) results from ice sublimation laboratory experiments;

2) models and results from thermodynamic and numerical simulations of dust/gas coma;

3) hints coming from models of cometary formations and evolution;

4) observational evidences concerning the activity mechanisms which includes:

  • a few direct measurements of DNCs at varying heliocentric distances;
  • in-situ measurements from previous space missions at comets for comparison and ground-truth;
  • overall results from remote-sensing instruments for other types of comets.

In particular, the aim of this ISSI International Team is to build up robust observational methods and modeling understanding to improve our capability to anticipate the activity levels and patterns of inbound DNCs in view of the Comet Interceptor mission.