Nitrogen and Oxygen Budget ExpLoration (NOBEL) M. Yamauchi (IRF, Kiruna, Sweden) I. Dandouras and H. Rème (IRAP, Toulouse, France) O. Marghitu (ISS, Bucharest-Magurele, Romania) and the NOBEL proposal team poster X4.283@ST3.3 (EGU2016-5530), Tuesday (2016-4-19)

Mission objectives Study thermal and non-thermal escape of major atmospheric elements (N and O) from the Earth. 1. Required observations: First-time exploration of the exosphere. First-time examination of isotope ratios in the magnetosphere/ionosphere. 2. Required measurement quality: Enable modeling of the escape on a geological time scale. Be a good reference in understanding the evolution of planetary atmosphere from the isotope ratio and N/O ratio. What is to be measured Density, fluxes, and energy-angle distribution for N+, N2+, O+, and H+ in the magnetosphere; Neutral and ion densities for N, N2, O, and O2 at exosphere/ionosphere (> 800 km); Isotope ratios of neutrals and cold ions (17O/16O, 18O/16O, D/H, and if possible 15N/14N, ) in the ionosphere, exosphere, and magnetosphere; for a wide range of solar wind and solar EUV conditions 2

Why exosphere? Mandatory for escape models (For thermal and some non-thermal escape) Poor knowledge (No knowledge of > 800 km for nitrogen, > 1500 km for oxygen, and all altitude for isotope ratio) Varies in both density/ionization (Mars observation indicates unknown factors other than EUV) Source of cold ions above the ionosphere (They contribute feeding ions of non-thermal escape) He < 800 km O < 700 km N2 < 500 km O2 One order of magnitude variation with only 20% change in Sun-Mars distance appear for only < 7 hrs 3

Why isotope ratios? Why nitrogen? Indicators of escape from planet (the isotope ratios are different between different escape processes) Isotope ratio of escape is unclear (mass-filter depends on ionization altitude) Poor knowledge (in the magnetosphere/ionosphere/exosphere) N2N2+N+ vs. O2O O+ (completely different solar/geomagnetic dependence) Scientifically important (a representative volatile, and essential for amino-acid formation) Escaped amount could be significant for biosphere (Escape matters for 5% change in atmospheric/oceanic O/N ratio, i.e., if ≥ 1026 ions/s in the past. Although a route from Ocean crust to Mantle is very large, escape to space alone can play role.) Not well known, but now possible to measure (impossible 5 years ago) light total estimated subduction of N from Ocean crust to Mantle is 9 x 1018 kg over 4 byr using current subduction rate. content in continental crust is 2 x 1018 kg, and 5 times(2x1019 kg) more inventory in the Mantle Mars atmosphere Earth Mars interior Jupiter heavy

Where is the optimum orbit? 1. Non-thermal escape can be estimated by covering both the exosphere and the inner magnetosphere. 2. ~100 km altitude resolution for both in-situ and remote sensing measurements of the exosphere within a single orbit

Payload S/C specification Baseline * Cold ion/neutral mass spectrometer (1) m/∆m ~ 2000 /slow (Bern) (2) m/∆m ~ 50 / fast (optional?) * Ion mass analyzers (0.01 – 30 keV): (1) m/q < 20 (Toulouse) (2) m/q > 10 (Kiruna) * Energetic Ion mass analyzer (UNH) * Magnetometer (Graz) * Langmuir probe (Brussels) * Electron analyzer (London) * UV spectrometer (U Tokyo) N+, N2+, N2, O+, O+ * Auroral / airglow camera (Tohoku) * Potential control (SC subsystem) Optional * Waves analyser with search coil (Prague and Orleans) * ENA monitoring (TBD) * IR emissions (if sensitivity is high) S/C specification outreach for camera attitude control Spin (22-26 sec) + despun platform attitude reference Sun-pointing resolution 1 min & 100 km angular resolution //, , and anti-//

Possible conjugate study Covering area of EISCAT_3D High sensitivity in more than 300 km diameter (white area) ≈ 10° longitudinal range.  3% of polar orbits traverse this region in average. With T~10 hours, NOBEL crosses once every 15 days in average. 7

Summary With recently developed reliable instrumentation, NOBEL will systematically study the exospheric conditions, nitrogen budget, isotope ratio of cold ions/neutrals above 1000 km. The knowledge is mandatory in estimating present-day’s thermal/non-thermal escape as well as behavior of the exosphere. The required instrumentation can also address extra science goals: Planetary Evolution: meaning of isotope ratio and N/O ratio. Exoplanet modeling: tuning interpretation of optical data on exoplanets by having both spectral and in-situ measurements. Ionosphere Physics: ionization chemistry, transport, and 3-D dynamics at its upper part together with EISCAT_3D. Inner Magnetospheric Dynamics: N+ as an independent tracer. Space Plasma Physics: different V0 for similar masses. 8

If maximum nitrogen escape is > 1028/s Comparable amount of escape between the Earth and Mars  The interpretation of isotope ratio (e.g., 15N/14N) is questioned.  Favors N2 delivery model than Outgassing model of NH3 unless escape mechanisms are different between the Earth and Mars. Two competing models of N2 + N2 delivery model (from comets, asteroids) Solving the problem that volatiles are difficult to be included in proto-Earth (Temprature/EUV) But amount of delivery is uncertain – Outgassing model of NH3 Nitrogen is expected in the proto-Earth (as NH3 rather than N2 due to higher temperature) But difficult to protect from hydrodynamic massive escape