Each of the four finalists, who were selected out of a group of 22, is set to receive $3 million in the coming year to develop their plans before two are selected for missions.
Triton, aptly named for the son of the Roman God of the sea, is a prime candidate for looking for signs of life in our solar system due to its icy seas. If life does exist outside of Earth, it could be hiding in subterranean oceans flowing under the surface of icy moons. The moon is located some 4.5 billion km (2.69 billion mi) away, and is considered an oddity given it orbits in the opposite direction of Neptune's 13 other moons.
Because its odd orbit, some experts think that this points to the planet originating from outside of our solar system, and the moon may be an "intruder" trapped long ago by Neptune's gravitational field.
The ISA and the Weizmann Institute of Science and Technology are part of a team planning a mission to Triton, called Trident, named after Neptune's three-pronged spear, that is slated for launch in 2026.
“The launch date is fixed by window of opportunity in which the configuration of the planets would enable a craft from Earth to reach Triton in just 12 years. The next window of opportunity will not come around until 2038," said Dr. Eli Galant, part of the development team.
If the proposal is approved, Trident would be the first Earthly visitor to Neptune and its moons in over thirty years. Hints of possible reserves of underground liquid were seen in "postcards" sent from the Voyager 2 mission, a probe launched by NASA in 1977, that sent back photos taken from over 40,000 km (24,854 mi) away from the moon.
Despite the distance, planetary scientists were able to observe that the surface of Triton is one of the most youthful seen in the solar system, suggesting intense suggesting intense geological activity. The proposed space mission will also be flying over, however this time at a distance of 500 km (310 mi).
It aims to investigate whether Triton does indeed have a subterranean ocean, study the properties of this ocean if it exists, and investigate why the surface looks so youthful and what makes up its atmosphere. Photos sent back from the Voyager showed the moon’s south pole revealed geysers spewing liquid nitrogen. This hinted at the possible existence of large underground reserves of liquid, as well as revealing the direction of winds and an atmosphere on the moon.
In order to help calculate the properties of Triton's atmosphere, a unique clock designed by Israelis on the mission team will be carried and used on the space craft.
The clock is so accurate it will lose less than a second in ten million years and is built to withstand the rigors of space travel over at least fifteen years.
The clock was designed by Professor Yohai Kaspi of the Weizmann Institute's Earth and Planetary Sciences Department and Galant, who were chosen for their experience in analyzing radio signals arriving from distant space craft. In this case, signals will be interpolated with the clock.
“This unique clock, developed for an ESA flagship mission, has raised interest with other mission teams. It is proof that Israeli industry and research have much to contribute to international space exploration," said Avi Blasberger, Director General of the ISA in Israel's Ministry of Science and Technology.
The Trident Mission is intended to be a smaller, cheaper, and shorter-term than larger NASA missions that take off once or twice a decade. Additionally, Discovery missions are all proposed, planned, and selected by researchers, in comparison to larger scale missions which may be chosen on the political or leadership level. The mission is led by Dr. Louise Prockter, Head of the Lunar and Planetary Institute in Houston Texas.