At the end of February / start of March 2017, NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. The workshop covered a number of ideas for the future exploration of the solar system using automated means.
Two of the more interesting areas of discussion were the exploration of the “ocean worlds” of the solar system, notably Jupiter’s Europa and Saturn’s Enceladus. The other was options for exploring Saturn’s moon Titan.
The “Icy Worlds”
As I’ve recently reported Europa is already the target of the upcoming Europa Multi Flyby mission, due to launch in the early 2020, and which is now known once more by its earlier title of Europa Clipper. However, at the workshop, scientists looked at future options for exploring it, starting with the lander mission already being planned as a follow-on mission.
What makes these icy worlds so interesting is that under their crusts of ice, there may well be oceans of liquid water. Europa and Enceladus in particular have demonstrated very strong signs that under a surface coating of ice, they have liquid water oceans, perhaps 100 km (62.5 mi) deep in the case of Europa.
These oceans are kept in a liquid state due to gravitational flexing: they are constantly being pulled in different directions by the gravities of their parent planet and the other moons in orbit around it. The flexing generates heat, and this heat could be sufficient to keep the water trapped under the ice crust of such a world in a liquid state. It could also mean that the ocean bed of such a world might be the locations of hydrothermal vents and fumeroles which are pushing out the heat, energy, minerals and chemicals needed to kick-start life.
Europa, Ganyemede and Callisto, around Jupiter show every indication of such sub-surface oceans, although Ganyemede’s and Callisto’s case, it might be more icy slush than liquid water. Both will be the subject of study by Europe’s Jupiter Icy Moons Explorer, due for launch in 2022.
Europa’s ocean is believed to be liquid both as a result of spectral analysis of the ice covering it, and because images of the moon captured by the Hubble Space Telescope appear to show huge geysers erupting from the moon’s south polar regions.
Geysers of water vapour have also been seen erupting from Enceladus by NASA’s Cassini mission, indicating it also has a liquid ocean under its covering of ice.
Worldlets like Ceres and Pluto also appear to have liquid interiors overlaying their cores, although the processes that might by allowing such liquid layers – likely water – have yet to be properly understood.
Of them all, Europa perhaps shows the strongest evidence for harbouring life-giving nutrients within its oceans, marking it as a prime candidate for study. This is because of the reddish-brown staining covering much of its surface. Most of this is likely debris from the huge volcanic eruptions which occur on Io, the innermost of the Galilean moons of Jupiter, and the one experiencing the greatest levels of gravitational flexing. However, some of Europa’s straining might be material deposited as a result of geyser action, particularly where the stains appear to run along many of the fault lines which crack Europa’s surface.
Given all this, planetary scientists are itching to get a vehicle onto the surface on Europa and – if possible, get one through the ice and into the ocean beneath it. Hence the discussions at the NASA workshop.
As I noted in writing about Europa Clipper (see the link above), a lander mission is already in the advanced planning stages thanks to strong support for missions to Europa in Congress. It could potentially take place just a couple of years after Europa Clipper arrives in orbit around Jupiter, and would have three mission objectives:
- Search for biosignatures and signs of life by analysing the surface and subsurface deposits on Europa, particularly recently erupted material near the lander’s location
- Analyse the composition of the surface ice and determine the proximity of liquid water beneath the ice
- Attempt to identify the dynamic processes responsible for shaping Europa’s surface and its properties.
If the lander mission detects signs of life or strong evidence of life-giving materials within Europa’s ice sheet, then it will likely pave the wave for the most ambitious mission of all: sending a vehicle to Europa with the means to penetrate the surface ice and release an automated submersible into the waters below to search for possible life.
While there is no time frame for such a mission, it has long been a goal for NASA and scientists. So much so that there have been numerous studies and even competitions for such vehicles, and a broad range of proposals and designs have been put forward. As such, it could be that such a mission could follow the Europa lander mission relatively quickly – perhaps within a decade.
By Air, By Sea: Exploring Titan
Titan, the largest moon of Saturn is of intense interest to scientists for three main reasons: it has a nitrogen-rich, thick atmosphere which has a comparable density to that of our own; it brings together an enticing mix of hydrocarbons which exist both on the surface as lakes and rivers and fall as “rain”; its surface appears to be massively rich in organic chemistry. All three present the kind of environment where all the prebiotic conditions needed to kick-start life may exist – the lack of liquid water notwithstanding.
In July 2016, I covered two concepts for exploring the lakes and rivers of Titan – NASA’s cancelled TiME (the Titan Mare Explorer) and Spain’s Titan Lake In-situ Sampling Propelled Explorer (TALISE), which has yet to receive support and funding. But at the NASA workshop mentioned at the top of this article allowed scientists to discuss some exotic concepts to explore Titan remotely.
One such idea could be the revival of the NASA / ESA Titan Saturn System Mission (TSSM) concept which offers the intriguing potential of placing a vehicle in orbit around Saturn where it would study the planet and its moons of Titan and Enceladus, and which would also act as the delivery craft for two missions to Titan.
The first of these would be a nuclear-heated balloon, the second, a lake lander similar in nature to the cancelled TiME mission. The balloon, designated by ESA as montgolfière in recognition of the Montgolfier brothers, would operate at an average altitude of about 10 km (6.25 mi) above the surface of Titan.
The gas inside the Balloon’s envelope would be heated by waster from the the small Radioisotopic Power System (RPS) – essentially a “nuclear battery” – which would generate the electricity for a suite of science instruments carried in a gondola suspended beneath the balloon. This instruments would sample the atmosphere, chart wind currents, monitor weather, and radar map the moon’s surface beneath the balloon in a mission which could last several years, with data being relayed by the TSSM main orbiter vehicle.
The lake lander, deployed separately to the balloon mission, would effectively be a re-vamp of the TiME mission. It would be designed to parachute down to a lake of liquid hyrdrocarbons called Ligeia Mare in Titan’s north polar regions. Once there it would drift on the currents, studying the chemistry, depth and marine processes of Titan’s seas, and examine Titan’s atmosphere for about 3-6 months.
Currently, TSSM isn’t funded as a mission, NASA having given priority to the Europa Clipper mission. However, were it to be fully revived, it could be launched via the Space Launch System in the late 2020s.
US Rocket Round-Up
SpaceX Readies Next Launch
Just four weeks after an inaugural Pad 39A launch at Kennedy Space Centre, SpaceX is readying its next launch from the historic launch complex – demonstrating it is on the road towards the goal of a launch every three weeks in the future.
Tuesday, March 14th is earmarked for the next Falcon 9 launch, which should deliver the EchoStar 23 communications satellite to geosynchronous orbit.
On Thursday March 9th, following its delivery to the launch pad, the rocket successfully completed a live fire of its first stage engines in preparation for the launch, an action which takes place prior to every Falcon 9 launch as a part of a full dress rehearsal for the actual launch.
Unlike other recent Falcon 9 missions, this flight will not see the recovery of the booster’s first stage, which will have to run longer in order to help deliver the payload to its required orbit, leaving the rocket stage with insufficient fuel to undertake the additional engine burns need for it to make a return to Earth and a safe landing.
Blue Origin Unveil New Glenn Rocket Engine
Blue Origin, the private space company headed by Amazon founder Jeff Bezos,unveiled the first BE-4 rocket motor to roll off of its new production line on Monday, March 6th.
The BE-4 is intended to power Blue Origin’s New Glenn family of boosters currently in development, and the Vulcan rocket being developed by United Launch Alliance (ULA).
Seven BE-4s will be used by the first stage of the New Glenn rocket, which will be recoverable after launch in much the same way as the first stage of s SpaceX Falcon 9. ULA’s Vulcan rocket will used two of the motors, supported by strap-on boosters, to power is core stage.
Neither the New Glenn nor the Vulcan launcher – both of which will eventually be rated for crew launches – will fly before 2019. In the meantime the new motor – and / or the two due to follow it off the production line – is likely slated for testing at Blue Origin’s test site in west Texas.
SLS 2nd Stage Arrives at Kennedy Space Centre
On Tuesday, March 7th, the first fully integrated element of America’s new Space Launch System (SLS) rocket arrived at Kennedy Space Centre, Florida. The interim cryogenic propulsion stage (ICPS) – that’s the rocket’s second stage to you and me – is designed and built by United Launch Alliance and Boeing. It will be used to power Orion missions away from Earth’s gravity.
The unit delivered to Kennedy Space Centre will form part of the first SLS rocket “stack” to be flown from the space centre’s Pad 39B as a part of Exploration Mission 1. Depending on the outcome of an in-progress NASA study, this flight will either take place in 2018, launching an uncrewed Orion vehicle on a flight around the moon, or will occurred in 2019 with a crew on board, also on a flight around the Moon.
NASA’s Lunar Space Station
NASA is moving ahead with plans to establish a “gateway” station in cislunar space where it could support crews working in lunar orbit or elsewhere in cislunar space for extended periods.
If built, the “gateway” station would be serviced by the Orion vehicle. In addition, NASA see the facility as being used to test technologies and perform other work needed to support long-term plans for human missions to Mars in the 2030s.
While an orbital facility around the Moon might be useful for lunar / cislunar operations, it would also appear to be adding a layer of complexity to such missions. Similarly, while the idea of using a facility orbiting the Moon to help “prepare” for missions to Mars might sound good, the reality is that most technologies required for a Mars mission could be tested just as efficiently – and more cost effectively and potentially safely – in Earth orbit. Thus, the “prepare for Mars mission” idea tends to sound more like an artificial justification for the “gateway” more than a genuinely needed precursor for sending humans to Mars.