Need for a mission to understand the Earth-Venus-Mars difference in Nitrogen

1. Need for a mission to understand the Earth-Venus-Mars difference in Nitrogen M. Yamauchi (IRF, Kiruna), I. Dandouras (IRAP, Toulouse), and the NITRO proposal team 4th SERENA – HEWG Meeting, Key Largo, May 2013

2. (A) Nitrogen as essential element of life Miller’s experiment (Miller and Urey, 1959). Model atmosphere + model lightning (discharge)  amino acid was formed! The result depends on the oxidation state of N reduced form (NH3) neutral form (N2) oxidized form (NOx)  Formation of pre-biotic molecules is most likely related to the relative abundance of N, O, and H near the surface (not only the amount!)

3. (B) N in the brother plants Earth: 75% of atmospheric mass (the amount in the soil, crust, and ocean are small) Venus ~ 2.5 times as much as Earth (3% of Patm.Venus = 90 x Patm.Earth) Titan ~ 1.5 times as much as Earth (98% of Patm.Titan) Mars ~ only 0.01%of the Earth (note: MMars ~ 10% of MEarth)

4. (B) N and O in the brother plants N is missing at Mars but O is abundant in all three planets (Martian case, exist in the crust as oxidized rocks)  Oxidation (O/N ratio for given Temperature) of planet is Mars > Venus > (Titan?) > Earth

5. Nitrogen (N/O ratio) Mystery N < 0.01% of Earth/Venus rich in N Venus Earth Mars N/O ratio at Mars << at the Earth, Venus, Titan

6. (B) N in the brother plants N/O ratio anomaly at Mars  A mystery in the solar system because (1) N is much more difficult to be ionised than O,due to the triple chemical binding (i.e., more difficult to escape). (2) The evolution model (Lammer’s model) cannot explain the N/O of both Venus and Mars simultaneously.

7. How about observation of escape? It is not easy to estimate the “value” of ancient abundance. However, tendency of N/O ratioof escape against solar forcing might be easier to obtain ( see example).

8. Example: guessing O+/H+ ratio ion escape H+< 50 eV O+< 50 eV H+> 10 eV O+> 10 eV High UV Low UV Akebono/SMS (Cully et al., 2003) Polar/TIMAS (Peterson, 2002)

9. Escape mechanisms

10. Dependence on the solar forcing Quick rotation of early Sun  stronger dynamo  stronger solar maxium  stronger CME Ancient? High UV flux of early Sun  expansion of the ionosphere beyond the magnetopause.  Treat as non-magnetized planet Ancient

11. Guessing escape (Non-Magnetised) Expected change in the escape of H, O, N (increase level +, ++, or +++) in response to enhanced external forcing. () means no relevant observation

12. Guessing escape (Magnetised) Expected change in the escape of H, O, N (increase level +, ++, or +++) in response to enhanced input from the sun

13. Present knowledge on N+ escape (1) Akebono (1989 launch): cold ions < 0.05 keV N+ N+ N++ N++ ram direction = ambient plasma // direction to B

14. Present knowledge on N+ escape More drastic change of N+ than O+ for < 0.05 keV N+ N+ N2+ But destination and acceleration is not clear

15. Present knowledge on N+ escape (2) AMPTE (1984 launch): energetic ions > 30 keV (Hamilton et al., 1988)

16. But no observations of N/O at 0.1 - 30 keV All past magnetospheric (and Mars / Venus) missions failed to separate N+ from O+at 0.05~10 keV range. This is because the time-of-flight (TOF) instruments use “start” foils, where ion energy losses (ion velocity scatter) merge the O+ TOF and the N+ TOF.

17. Technology is within reach! MEX / IMA, IRF

18. Technology is within reach! MEX/IMA detected C+/N+/O+ group in 4 mass channels (ch.10, 11, 12, 13) out of total 32 channels. * IMA uses only 5 cm magnet to separate mass-per-charge, and by doubling the magnet to 10 cm, we could separate C-N-O.

19. CESR/IRAP Time-of-Flight R&D: Grazing-incidence MCP as “start foil” Beam energy of 10 keV P. Devoto, J.-L.Médale, and J.-A. Sauvaud, Rev. Sci. Instru., 2008

20. Need for a mission (1) Understanding the non-thermal nitrogen escape is important in modeling both the ancient atmosphere of the Earth and the Martian nitrogen mystery. (2) Unfortunately, past magnetospheric missions could not separate N+/O+ for > 50 eV because of high cross-talk in TOF instruments. (3) Now, the technology to separate N+ and O+ with light-weight instrument just became available. (4) Therefore, we need a dedicated mission to understand N+. This is the Nitro mission, that was proposed to ESA.

21. Mission orbit and Payload North In-situ obs. All types of ion mass analysers: (1) Magnet (2) Grazing-incidence MCP as “start foil” (3) Shutter TOF (4) Reflection TOF (various types) Imaging ENA of 1-10 keV (substorm injections) Optical (emission) (1) N+ : 91nm, 108nm (2) N2+ : 391 nm, 428nm (3) NO+ South

22. cf. Auroral N2+ emission e- collisions ionise N2to make exited N2+ that emits blue line (but N2 is exited or even N2+ pre-exists by solar UV during equinox)

23. Spin-offs of N & O observations

24. Qualitative differences between O+ & N+ (1) Transport: Magnetospheric Physics H+ O+  How about N+ and N2+?

25. In-situ Payload Requirements #1: N+- O+ separation (M / ∆M ≥ 8 for narrow mass range) and H+- He+- O+ separation (M/∆M ≥ 2 for wide mass) at  and // directions at 10-1000 eV (11 km/s~9 eV for N) with ∆E/E ≤ 7% ((EO+-EN+) / EN+ = 15%).

26. Nitrogen is our future Nitrogen is an essential element of life N/O ratio is quite different between brother plants No observations of N+/O+ ratio at 0.1 - 10 keV range  New Mission with the first-time measurement of N+ and N+ / O+ ratio of the escape (>50 eV) for interdisciplinary purposes: (a) History of oxidation state of the atmospheric nitrogen, (b) Mars mystery on N/O ratio, (c) ion injections and dynamics in the magnetosphere (d) acceleration mechanisms, (e) re-distribution of energy in the upper ionosphere.

27. N/O ratio at Mars << at the Earth, Venus, Titan: We Need a Nitrogen mission Proposal for a Small Mission, submitted to ESA: June 2012 “Quad Chart” submitted to NASA (Heliophysics): January 2013 Preparation for a proposal to ESA, in response to the forthcoming M-4 call.