REHOVOT, ISRAEL—May 14, 2020—An incredibly accurate clock planned by the Weizmann Institute of Science, the Israel Space Agency (ISA), and an Israeli company could be on its way to Neptune’s largest moon in 2026.
If life does exist outside of Earth in our Solar System, it could be hiding in subterranean oceans flowing under the surface of icy moons. One of the most promising candidates for such an underground liquid body is Triton – aptly named for the son of the sea god Neptune, the planet around which it orbits. Triton, Neptune’s largest moon, some 4.5 billion km (2.8 million miles) away, is an oddity: it orbits in the opposite direction from all of Neptune’s other moons. Some think this points to an origin outside of our Solar System: the moon may be an intruder that was trapped long ago by Neptune’s gravitational field.
The Weizmann Institute and ISA, which is in Israel’s Ministry of Science and Technology, are part of a team planning a mission to Triton. Called Trident, for Neptune’s three-pronged spear, the mission is slated for launch in 2026. As a finalist in NASA’s Discovery Program, Trident joins three other proposals, each of which will receive $3 million dollars in the coming year to develop their plans before two are ultimately selected. The four finalists were chosen from 22 proposals.
If successful, Trident would be the first Earthly visitor to Neptune and its moons in more than 30 years. The last “postcards” from Neptune were from Voyager 2, which sent back photos taken 40,000 km (24,850 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 – just a few million years old – suggesting intense geological activity. And photos of the moon’s south pole revealed geysers spewing liquid nitrogen, hinting at the possible existence of large underground reserves of liquid, as well as revealing the direction of winds and an atmosphere on the moon.
Trident will also be flying over Neptune – but from a distance of only 500 km (about 310 mi). Prof. Yohai Kaspi of the Institute’s Department of Earth and Planetary Sciences is part of Trident’s science team, which is led by Dr. Louise Prockter, head of the Lunar and Planetary Institute in Houston, Texas. The proposed space mission 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.
Prof. Kaspi and his group member Dr. Eli Galanti are on the team because of their experience in analyzing radio signals arriving from distant spacecraft, which in this case will be interpolated with a special clock they designed that will be carried on the spacecraft – a clock so accurate that it will lose less than a second in 10 million years and built to withstand the rigors of space travel over at least 15 years.
The clock will be built in Jerusalem by the firm Accubeat and funded by the ISA. Prof. Kaspi and Dr. Galanti will use the clock to calculate the properties of Triton’s atmosphere, based on the Doppler displacement of radio waves beamed back to Earth from the spacecraft. The Israeli-made clock will assist them in measuring minute oscillations in these waves.
A similar clock is already in advanced stages of preparation at Accubeat, and will be launched aboard the European Space Agency’s (ESA’s) JUICE mission to the moons of Jupiter, set for 2022. Calling it the most accurate clock of its kind, Prof. Kaspi says: “There are more exact clocks than the one we will be launching, but those are very large and stationary.”
Avi Blasberger, Director General of the ISA, adds: “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.”
In addition to the clock – which will be operated by the Israeli team – the Trident craft, if chosen, will carry a magnetometer for seeking out the underground ocean; two kinds of spectrometers – one infrared to examine the surface and the other plasma for determining the makeup of the atmosphere; and two kinds of cameras that will also be trained on regions of Neptune that have never before been observed.
As part of NASA’s Discovery Program, the Trident mission is intended to be smaller, cheaper, chancier, and shorter-term than the large missions that take off once or twice a decade. Unlike large missions that may be chosen on the political or leadership level, the Discovery missions are all proposed, planned, and selected by researchers.
Dr. Galanti adds that the mission depends on its being chosen within the next year: “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.”
Prof. Yohai Kaspi’s research is supported by the de Botton Center for Marine Science; the André Deloro Institute for Space and Optics Research; and the Schwartz/Reisman Institute for Theoretical Physics.
