Since the February 2017 announcement on the discovery of seven rocky planets orbiting the nearby red dwarf star TRAPPIST-1, multiple studies have been conducted to ascertain whether any of the planets might harbour conditions suitable for life. The nature of their parent star would suggest this to be unlikely. However, an international team utilising the Hubble Space Telescope (HST) to study the TRAPPIST-1 system believe they’ve found evidence that some of the planets have the right conditions to allow liquid water to exist.
Vincent Bourrier, from the Observatoire de l’Université de Genève in Switzerland, and his team used the Space Telescope Imaging Spectrograph (STIS) to study the amount of ultraviolet radiation each of the TRAPPIST-1 planets receives. If there were too much UV light, no water could survive on the surface because the water molecules would break up and escape through the top of the atmosphere as hydrogen and oxygen gas.
The team found that the inner planets in the system – TRAPPIST-1b and 1c – receive so much UV radiation from their sun, they may have lost more than 20 Earth-oceans worth of water in the course of their history, estimated to be between 5.4 and 9.8 billion years old. Thus, they are almost certainly devoid of water, and their surfaces are likely sterile. However, the findings also suggest the outer planets in the system – including the three within TRAPPIST-1’s habitable zone, may have lost less than three Earth-oceans’ worth of water throughout their history, and could possibly still possess liquid water, making them more amenable for life to rise.
As well as suggesting some of the TRAPPIST-1 planets may have liquid water present, the study has broader implications for the potential of other exoplanets harbouring life. Up to 70% of the stars in the Milky Way are believed to by M-class red dwarfs – and the majority of rocky exoplanets thus far found are orbiting such stars. So this study might indicate that many more of the exoplanets orbiting such stars could support liquid water and, perhaps, conditions suitable for life. However Bourrier and his colleagues emphasise that the study is not conclusive, and further research is needed to determine if any of the TRAPPIST-1 planets are actually watery.
SNC Prepares Dream Chaser for Glide Flight Testing and UN Mission
Sierra Nevada Corporation (SNC) carried out a “captive / carry” test of a Dreamer Chaser Cargo vehicle test article on August 31st, 2017. The flight, with the vehicle slung beneath a helicopter forms the first step towards the Dream Chaser Cargo carrying out glide flights and landings.
During the test, SNC collected data on the vehicle’s performance in flight, including operation of radar altimeters, air data probes and other systems that cannot be fully tested on the ground. The captive / carry test followed a series of ground tests where the vehicle was towed behind a truck down a runway at speeds of up to 100 kph to ascertain its ground handling on landing.
SNC developed Dream Chaser to transport astronauts to and from the ISS. However, NASA selected capsule designs by SpaceX and Boeing. After a protest over the decision, filed with the U.S. Government Accountability Office, failed, SNC turned their attention to other potential uses for Dream Chaser.
One of these has been the development of a cargo variant to service the International Space Station (ISS) alongside existing resupply contractors, Orbital ATK and SpaceX, and in 2016, NASA confirmed Dream Chaser Cargo has been selected to fly resupply missions to the ISS between 2019 and 2024.
On July 19th, 2017, it was announced that SNC had signed a contract with United Launch Alliance for the first two launches of these resupply missions, using the Atlas 5 552 launch vehicle. The first launch is scheduled for 2020 and the second in 2021, although NASA has yet to formally order any Dream Chaser flights.
A Dream Chaser Cargo vehicle will also be used in 2021 to launch the first United Nations mission into space. The United Nations Office of Outer Space Affairs (UNOOSA) said an agreement between them and SNC to fly the dedicated Dream Chaser mission is part of a broader effort by the office to increase access to space to emerging nations.
The mission will be open to all nations, but with a particular emphasis on those that don’t have the capabilities to fly their own experiments in space. UNOOSA are in the process of soliciting payload proposals with a goal of selecting payloads by early 2018 so that the winning countries have time to build them for a 2021 launch.
Unlike the majority of Dream Chaser Cargo missions, which will focused on ISS resupply work, the UNOOSA flight will see the vehicle placed in orbit around the Earth, and SNC have indicated the vehicle will be capable of operating freely in orbit for extended periods of time, should the UN desire a longer mission.
While billed as the UN’s first space mission, the Dream Chaser flight is part of UNOOSA’s Human Space Technology Initiative, launched in 2010 with the goal of providing developing countries the possibility to access space in microgravity conditions. Currently, the initiative includes two other major projects. The first is a cooperative project with the Japan Aerospace Exploration Agency (JAXA), designed to give developing nations the opportunity to launch cubesats from the ISS. Another programme, to be operated in cooperation with China’s space programme, will allow UN-backed missions to be flown aboard China’s space station, when it becomes operational in 2020.
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