''Castalia'' is a proposed mission concept for a robotic spacecraft to explore the

main-belt comet Active asteroids are Small Solar System body, small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a Coma (cometary), coma, comet tail, tail, or other visual evidence of mass-loss ...

7968 Elst–Pizarro Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets, and is the prototype of active asteroids. Its orbit keeps it within the asteroid belt, yet it displayed a dust tail like a comet while near perihelion in 1 ...

and make the first ''in situ'' measurements of water in the asteroid belt, and thus, help solve the mystery of the origin of Earth's water. The lead is Colin Snodgrass, from

The Open University The Open University (OU) is a Public university, public research university and the largest university in the United Kingdom by List of universities in the United Kingdom by enrolment, number of students. The majority of the OU's undergraduate ...

in UK. ''Castalia'' was proposed in 2015 and 2016 to the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

within the Cosmic Vision programme missions M4 and M5, but it was not selected. Because of the construction time required and orbital dynamics, a launch date of October 2028 is proposed.

Overview

Main-belt comet Active asteroids are Small Solar System body, small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a Coma (cometary), coma, comet tail, tail, or other visual evidence of mass-loss ...

s (MBCs) are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. The ''Rosetta'' mission to comet

67P/Churyumov–Gerasimenko 67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C–G) is a Jupiter-family comet. It is originally from the Kuiper belt and has an orbital period of 6.45 years as of 2012, a rotation period of approximately 12.4 hours, and a maximum velo ...

in 2014, indicates that Jupiter family comets cannot be the main source of Earth's water as previously thought. ''Castalia'' would rendezvous and orbit comet

and measure

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

ratios, plasma and dust properties, while also mapping its interior structure with a radar. Basically, ''Castalia'' would test whether MBCs are a viable source for Earth's water, and to use MBCs as tracers of the

formation and evolution of the Solar System There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while ...

. The mission architecture and spacecraft design were initially developed in 2013 by the

German Aerospace Center The German Aerospace Center (, abbreviated DLR, literally ''German Center for Air- and Space-flight'') is the national center for aerospace, energy and transportation research of Germany, founded in 1969. It is headquartered in Cologne with 3 ...

(DLR) in Bremen and

OHB SE OHB SE, headquartered in Bremen, is a European space and technology group specializing in the development and implementation of complete space systems, the production of components for various launcher programs as well as the operation of satell ...

. ''Castalia'' was proposed, in slightly different versions, to the

M4 (2015), and M5 (2016) missions within the Cosmic Vision programme. Although it was not selected, the team continues to mature the mission concept and science goals. The mission concept is named after

Castalia Castalia (), in ancient Greek and Roman literature, was the name of a spring near Delphi, sacred to the Muses; it is also known as the Castalian Spring. It is said to have derived its name from Castalia, a naiad-nymph, daughter of the river-g ...

, a nymph in Greek mythology that was turned into a fountain by a god, and she could inspire the genius of poetry to those who drank her waters or listened to their quiet sound.

Science goals

The main science goals of the mission are: *Characterise a main belt comet (MBC), by ''in situ'' investigation *Understand the physics of MBC activity *Directly detect water in the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

*Test whether MBCs are a viable source for Earth's water *Use MBCs as tracers of planetary system formation and evolution.

Science payload

The conceptual science payload includes the following instruments: *MBCCAM, vis/near-IR imager *TMC, thermal IR imager *SOURCE, deep radar *SSR, shallow radar *CAMS,

mass spectrometer Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is us ...

*DIDIMA, combined dust detector and composition *MAG,

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...

*ChAPS, plasma package The mission would also include a

radio science One way of outlining the subject of ''radio science'' is listing the topics associated with it by authoritative bodies. Union of Radio Science International (URSI) The International Union of Radio Science has several commissions corresponding t ...

experiment using the spacecraft's communication system.

References

{{European Space Agency European Space Agency space probes Proposed spacecraft Missions to comets

Overview

Science goals

Science payload

See also

References