Europa Lander (NASA)

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Artists's concept of the NASA Europa Lander
Another view with planet Jupiter in the background
Europa
One of the closest views yet of Europa's surface, as seen during the closest Galileo flyby
On Earth, subglacial microbial communities at Blood Falls survive in cold darkness without oxygen, living in brine water below Taylor Glacier, but come out at this location in Antarctica. The red color comes from dissolved iron.

Europa Lander is a proposed spacecraft concept by NASA for a lander for Jupiter's moon Europa.[1][2]

History and goals

The United States Congress issued a congressional directive about a Europa Lander, and NASA formed a response in 2016, assessing and evaluating the concept.[1] The NASA planetary panel delivered its report in early February 2017.[1] This was a six-month long study to produce the concept.[3] It was produced by what is called a Science Definition Team or SDT.[4] NASA has not decided on actually flying the mission, it is only a concept as of the late 2010s, however it could lead to an actual mission.[4] This study is for separately launched lander, as previously NASA did consider a lander for an orbiter mission, but this in particular was to respond to the government's specific mandate for a Europa lander to be evaluated.[5]

The mission has three main science goals:[6]

  1. search for evidence of life on Europa
  2. assess the habitability of Europa by directly analyzing material from the surface
  3. characterize the surface and subsurface for future missions

The concept would require further development to be launched, but one of the instrument candidates is a drill, and another requirement is to operate in the radiation environment at the moon's surface.[3] The radiation environment at Europa is extreme, and the publication Popular Science suggested that the lander may need a radiation vault like the Juno Jupiter orbiter.[7] The Juno Radiation Vault helped reduce radiation exposure to vulnerable systems, especially electronics on the orbiter.

The primary mission goal is life-detection, the first time in forty years that a NASA mission would have a life-detection strategy evaluated as a main goal.[1][8] The last time was the Viking program in the 1970s.[1] (see Viking lander biological experiments) The lander was described as a logical follow-up to the Galileo orbiter and probe mission, for which a major result was the discovery of conditions on Europa that may support life— in particular a large sub-surface ocean.[3] Earth life can be found in essentially all locations where water is present (liquid H2O). It follows that Europa is an excellent candidate in the search for life elsewhere in the Solar system.[9] This subsurface water may not only be warmed by geological activity, but likely also enriched with dissolved minerals and organic compounds.[10] Various ecosystems exist on Earth without any access to sunlight relying instead on hydrothermal vents or other sources of chemicals suitable to energy production by extremophiles.[11] (see chemosynthesis) Measurements to date indicate that Europa has an ocean approximately twice the volume of Earth's oceans. This water layer below the ice may be in contact with the moon's interior allowing ready access to hydrothermal energy and chemistry.[6] Europa surface missions can take advantage of the relatively young, active surface of Europa as this activity may allow deep subsurface materials to regularly escape to the surface.[12]

NASA had previously evaluated a Europa Lander concept in 2005 with the Europa Lander Mission concept.[13] Also, a lander was evaluated in 2012.[14] There was continued support for Europa missions, including in 2014, when the U.S. Congress House Appropriations Committee announced a bipartisan bill that included $80 million USD in funding to continue the Europa mission concept studies.[15][16]

Major stages of the Europa Lander mission:[17]

  • Cruise and relay communications spacecraft
  • De-orbit stage
  • Descent stage
  • Landing stage

The Europa Clipper, if it was still operating, could function as an additional relay communication spacecraft for the lander.[17]

Instruments

Possible equipment/instrument payload:[4]

Some instrument suites that have been proposed for a Europa lander include mass spectrometer, magnetometer, seismometer, imaging system, Raman spectrometer, and a microscopic imager.[18]

Launch and trajectory

The launcher has to be the Space Launch System, with a potential launch sometime in the 2020s.[4] No other launch vehicle has the performance to launch the lander mission given the spacecraft's mass of 16.6 metric tons.[19] One calculated trajectory would see a launch aboard SLS in 2025, Earth gravity assist in 2027, and Jupiter/Europa arrival in 2030.[4] It would spend some time orbiting around Jupiter over the next year to maneuver for its landing on Europa.[4]

Landing

At Europa it would have to land on the surface, matching its velocity, but with essentially no atmosphere there is no "entry", it is just a descent and landing.[17] The Planetary Society noted that NASA called this DDL— de-orbit, descent, and landing.[17] Discovered in 1995 by the Hubble Space Telescope, Europa has a very tenuous atmosphere of oxygen,[20] compared to Earth, it is extremely tenuous, the pressure at the surface is predicted to be 0.1 μPa, or 10−12 times that of the Earth.[21]

Power on surface

Once landed, it would likely operate for about 20 days by using chemical battery power, rather than a radioisotope thermoelectric generator (RTG) or solar power.[4] One problem with nuclear power is availability: As of 2015 NASA has only enough Pu-238 to power four RTGs.[22] While the Department of Energy began manufacturing Pu-238 again in 2013, NASA is saving its limited supply for other applications such as Voyager-like spacecraft or Mars rovers.[22] The RTGs are famous for powering spacecraft for decades; for example, the Voyager program probes that were designed and launched in 1977 are still operational.[22] On the other hand, solar panels would have to receive enough sunlight and endure the radiation environment. One issue is that solar panels can be significantly degraded by radiation.[23] Previously, NASA had evaluated a nuclear powered add-on Lander to the cancelled Jupiter Icy Moons Orbiter mission, which might have used a small radioisotope power system (RPS) for power.[24] Regardless of the power source, one of the limiting factors for the lifetime of the mission may be surviving radiation; the surface of Europa is predicted to experience 540 rem per day, whereas a typical Earth surface dose is about 0.14 rem/day.[25] Radiation damaged the electronics of the Galileo orbiter during its mission.[26] In 2012 a nuclear powered Europa Lander was evaluated, which would have used two ASRGs.[14]

Europa Clipper

The Europa Clipper is a separately launched spacecraft that would lay a foundation for the Europa Lander mission.[27] Previously, NASA had evaluated a lander for that mission as well, but the strong congressional support led to a full separate mission proposal for the lander by 2016.[5] The orbiter/flyby mission is important for a Europa lander in that it will help determine a landing location and prepare the way for it.[28] Also in February 2017 the EMFM moved from Phase A to Phase B, which includes the selection of instruments.[29] On March 9, 2017, NASA officially named the EMFM mission the Europa Clipper.[30]

The budget for the next year did not include funding for the Europa Lander concept, however, there was continued support for the SLS on which the Europa Lander would probably need.[31][4] Also, there was continued funding for the Europa Clipper.[31]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ JPL moves ahead with Mars and Europa missions despite funding uncertainty. Jeff Foust. July 18, 2017.
  3. ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ [1]
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ 14.0 14.1 [2]
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ 17.0 17.1 17.2 17.3 Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ 22.0 22.1 22.2 Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ [3]
  24. ↑ Abelson & Shirley – Small RPS-Enabled Europa Lander Mission (2005). (PDF) . Retrieved on 23 July 2013
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ [4]
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  28. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  29. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  30. ↑ [5]
  31. ↑ 31.0 31.1 [6]

External links

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