Four suspects beyond Earth: places in our solar system with life?

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1 Four suspects beyond Earth: places in our solar system with life? Mars Follow the methane Europa Enceladus Look for organicfilled cracks Sample plume for life signs Tita n Sample surface methane seas for exotic life

2 We will be examining two moons natural satellites of Jupiter and Saturn, in this case that lie outside the classical habitable zone but might have oceans of liquid water beneath their surfaces. Europa, a moon of Jupiter and Enceladus, a moon of Saturn. hab zone from psu.edu

3 Europa and Enceladus Europa Moon Earth Enceladus

4 Io Europa Ganymede Callisto The Galilean system of Jupiter: Europa is 10% smaller than our Moon Moon (Luna)

5 Object Semi-major axis Sidereal period Io 422,000 km days Europa 671, Ganymede 1,070, Callisto 1,883, The periods of the three inner Galilean moons are simple integer multiple of each other, maintaining their orbits to be ellipses rather than circles, and hence setting them up for tidal heating.

6 Tidal effects are the result of the gradient or change with distance of the gravitational force. Gravitational force goes as the inverse square of distance. The tidal force goes as the inverse cube of distance.

7 Europa is 1.5 times farther from Jupiter than Io. It feels less than 1/3 the tidal force than does Io, and gets much less tidal heat: just enough for warm ice (top figure), or plenty for a liquid ocean (bottom figure)?

8 Galileo Jupiter Launch October 1989 Arrival at Jupiter: December 1995 End of mission: September 2003

9 Galileo discovered a liquid water layer under the surface of Jupiter s moon Europa in 1998 Galileo images showed: weird ice geology plates of ice broken apart and rotated circumstantial evidence for an ocean past or present 9

10 More unusual geology fractures overlying fractures. This is evidence for a thin, active crust. 10

11 Magnetic field measurements gave the answer: Europa generates an induced magnetic field as it plows through Jupiter s magnetic field. Kurana et al Theory Electric motor This requires a highly electrically conducting layer beneath Europa s ice crust salty water. Smoking gun for a salty subsurface ocean on Europa! 11

12 Magnetic field measurements gave the answer: Europa generates an induced magnetic field as it plows through Jupiter s magnetic field. Kurana et al Theory Galileo measurement This requires a highly electrically conducting layer beneath Europa s ice crust salty water. Smoking gun for a salty subsurface ocean on Europa! 12

15 But we still do not know how thick is the ice crust. These cycloidal fractures say thin (hundred meters). this impact crater, 30 km across with a peak 600 meters high, says thick (10 km).

16 Exploring Europa: Europa at 6 m resolution (bottom of image) Where s your landing site? Where do you set up the drill? To which ridge do you anchor? We re not ready to get down into the ocean.

17 Europa Mission Scientific Instrument(s) - Plasma Instrument for Magnetic Sounding (PIMS) - Interior Characterization of Europa using MAGnetometry (ICEMAG) - Mapping Imaging Spectrometer for Europa (MISE) - Europa Imaging System (EIS) - Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) - Europa THermal Emission Imaging System (E-THEMIS) - MAss SPectrometer for Planetary EXploration/Europa (MASPEX) - Ultraviolet Spectrograph/Europa (UVS) - SUrface Dust Mass Analyzer (SUDA)

18 MISE Science Goals Goal 1: Assess the habitability of Europa s ocean by understanding the inventory and distribution of surface compounds. Goal 2: Investigate the geologic history of Europa s surface and search for areas that are currently active. MISE will produce maps of key compounds to answer questions about Europa s ocean and it s habitability Links surface geology and composition. Organics Salts Hot Spots Ices Does Europa s ocean have organics? What does surface chemistry tell us about habitability? Is Europa How do changes currently active? in ice crystal structure relate to the age of Europa s surface? 18

20 on meaningful spatial scales Local < 25 m / pixel Regional < 300 m / pixel Global < 10 km / pixel 20

23 Enceladus: It s been a more than quarter-century journey 1981: Voyager 2 reveals a smooth surface. Attempts to search for plumes are unsuccessful.

24 Cassini-Huygens Launch Oct 1997 Arrival July 2004 End Sept. 2017

25 2005: Cassini discovers the plumes and the south polar fracture system but is the source liquid water or warm ice?

27 Cassini measures composition with a mass spectrometer

28 2008: Cassini discovers organics, ammonia in the plume by flying through plume and analyzing the material with its mass spectrometer. Waite et al, Nature, 2009.

29 : Cassini finds sodium and potassium salts in the plume material High heat flow from the south polar region measured by Cassini Conclusion is that it s liquid water, with salts and organics, but how much? Is it long lived?

30 April Cassini discovers a regional sea beneath the South Pole: the smoking gun that the jets are underlain by a long-lived liquid water region making plausible the idea that life exists there: Liquid water Organics Nitrogen Salts Energy

31 2014-5: Regional Sea under the Ice Cassini radio science combined with topography and rotational data discovers a global ocean, perhaps thicker at the south pole: the smoking gun that beneath the jets is a region of liquid water, stable for very long time periods. Iess et al., Science; McKinnon 2015; Thomas et al. 2015, Icarus

32 Nanometer-sized silica-rich grains detected by Cassini CDA suggest hot water in Enceladus (Hsu et al 2015)

33 On the possibility of life on Enceladus. Organisms exist on the ocean floor of the Earth, fed by chemical differences between hot hydrothermal vents and the surrounding seafloor. The photos show carbonate deposits at the vents. As one example of food produced without sunlight, methane is made in the crust below the vents from reacting water and carbon dioxide mediated by rock, a process called serpentinization. The methane can be used by certain organisms as food. This might happen at the base of the Europa ocean.

34 Porco and Nimmo 2014

35 An example of one of the fissures or sulchi from which the jet emanate. The crack is about twenty meters across

36 Life in Enceladus? Multiple factors make plausible the idea that life exists there: An accessible, salty (CDA) ocean (RSS+ISS) Organics (INMS) Energy (CIRS) Hydrothermal system at ocean base (CDA)

40 ELF uses advanced mass spectrometers to do what Cassini can t

41 Amino acid pattern deviating from abiotic ELF's three tests for biological processes: Put simply: Glycine and Alanine dominate in abiotic systems, but not in biotic systems.

42 ELF's three tests for biological processes: Amino acid pattern deviating from abiotic Repeating subunits and clustering in membrane-building molecules Put simply: biotic membranes exhibit repeating carbon subunits; abiotic do not.

43 ELF's three tests for biological processes: Amino acid pattern deviating from abiotic Repeating subunits and clustering in membrane-building molecules Combined isotopic and compositional trends

44 A fourth independent test, carried as a technology demonstrator, measures the entantiomeric ratios of chiral amino acids are they overwhelmingly left- or righthanded, or a mixture? This. or that or both? Enceladus Organics Analyzer (EOA)--microchip capillary electrophoresis: Provided by Dr. Richard Mathies at UC Berkeley

45 ELF not selected Rembrant, Jeremiah Lamenting the destruction of Jerusalem

Chapter 7 Our Planetary System. What does the solar system look like? Thought Question How does the Earth-Sun distance compare with the Sun s radius

Chapter 7 Our Planetary System 7.1 Studying the Solar System Our goals for learning:! What does the solar system look like?! What can we learn by comparing the planets to one another?! What are the major