There was more than a little outcry over the selection of the InSight mission to Mars over two other very attractive missions when the choice was made in August of this year. One of the two missions not selected – was the Titan Mare Explorer or “TiME.” TiME would have seen a probe sail on the surface of one of the methane seas of Saturn’s moon Titan.
It would have been the first nautical exploration of an alien sea, but it was not to be – at least not yet.
The TiME mission was proposed after it was confirmed that Titan indeed contained rivers, lakes and seas consisting of liquid methane. The target was the methane lake Ligeia Mare, which is larger than Lake Superior on Earth. Ligeia has a total surface area of approximately 100,000 km2. If for some reason this wasn’t possible, a backup site had also been selected, Kraken Mare.
Missions to land on one of Titan’s lakes were also proposed under the Solar System Decadal Survey and is still being considered for the Titan-Saturn System Mission which could launch sometime in the 2020s. In 2012 a similar project was announced in Europe, the Titan Lake In-situ Sampling Propelled Explorer or “TALISE.”
Unlike the Huygens probe which landed on the Titan surface in 2005, TiME would have relayed its findings directly back to Earth. Huygens transmitted its findings to the orbiting Cassini spacecraft which then sent that information back home. Line-of-sight communication with Earth will not be possible between 2026-2035 as Earth will have dipped below the horizon at the Ligeia Mare site.
Why explore the lakes of Titan?
Simply put, Titan, the only moon in the solar system with an appreciable atmosphere, is like a flash-frozen young Earth. With organic compounds, hydrocarbons, possible cryovolcanoes, methane rain and other features that bear a striking resemblance to terrestrial processes – exploring Titan could provide new insights about how life got started on Earth.
Titan is the second-largest moon in our solar system, behind Jupiter’s Ganymede. Whereas Earth has a hydrological cycle Titan has a methanological cycle (according to Professor Brian Cox on the television show Wonders of the Solar System). However, Titan is only somewhat similar to our world. With gravity far less than Earth’s, the droplets of methane rain are much larger than rain on Earth and fall at a far slower rate, one that resembles snow. Water on Titan behaves more like stone as temperatures drop to around -180 °C.
TiME would have had Ellen Stofan, a member of the Cassini mission’s radar team, as its principal investigator. The Applied Physics Laboratory (APL) would have managed the mission. Lockheed-Martin would have built the vessel with instruments provided by NASA’s Goddard Space Flight Center, APL and Malin Space Science Systems.
The science that would have been conducted on TiME would have been revolutionary. Scientific measurements would have begun on descent to the Moon’s surface and would have been included the following; determine the depth of a Titan sea, what chemistry is taking place there, discover Titan marine processes and study the atmosphere above the sea.
The tech that would have been employed on this mission would also have been cutting edge.
Titan’s atmosphere is thicker than Earth’s and this precluded the use of solar panels on TiME. Batteries would have only provided a few hours worth of power, so, if the mission had been given the green light, it would have been the first mission that employed the Adanced Stirling Radioisotope Generator (ASRG). This prototype system is expected to be as much as four times more efficient than current radioisotope thermoelectric generators (RTGs).
The mission was not without its potential technical pitfalls however.
The boat would have been unpowered. It would have been at the mercy of Ligeia Mare’s currents and winds. Anyone who has toyed with a remotely-controlled boat and left it alone knows what normally happens. The boat can get stuck, immobile and goes nowhere. This was deemed to not be an issue as it was felt that TiME would have been pushed around for months by Ligeia Mare’s currents.
TiME would have launch on a United Launch Alliance (ULA) Atlas V 411 rocket in 2016 arriving at the smoggy moon in 2023. TiME was one of three missions selected under the Discovery Program receiving $3 million in May of 2011 when it was selected as a finalist. The other two missions chosen were the aforementioned InSight mission to Mars and the Comet Hopper or “CHopper” mission that would have followed a comet as it traveled throughout the solar system. NASA chose InSight in Aug. 2012. TiME was a proposal made by Proxemy Research with a cost capped out at $425 million (excluding the launch vehicle).