1. M. Yamauchi, I. Dandouras, H. Rème, and the NITRO Proposal Team ESWW-11, Liège, November 2014 Planetary Space Weather Session Nitrogen Ion TRacing Observatory (NITRO): Toward understanding the Earth-Venus-Mars difference of N/O ratio

2. Nitrogen in Planetary Atmospheres VenusEarthMars Titan ~ 2.5 times as much as on Earth 3% of P atmo.Venus x 90 P atmo.Earth 75 % of the atmospheric mass ~ only 0.01% times as much as on Earth (M Mars ~ 10% M Earth ) ~ 1.5 times as much as on Earth 98 % of P atmo.Titan rich in N N < 0.01% of Earth Venus Earth Mars Understanding the Nitrogen distribution around Earth and the differences of N / O between the sister planets

3. Molecular dissociation energy : N 2 : 945 kJ/mole (9.79 eV) O 2 : 497 kJ/mole (5.15 eV) H 2 : 436 kJ/mole (4.52 eV) Ionisation energy: N: 1402 kJ/mole (14.53 eV) O: 1314 kJ/mole (13.62 eV) H: 1312 kJ/mole (13.60 eV) Nitrogen Escape  Nitrogen is much more difficult to be dissociated (triple bond) and ionised  More difficult to escape  The atmospheric evolution model (Lammer’s model) cannot explain the N / O ratio of Venus and Mars simultaneously  It is not easy to explain the evolution of the abundances  The key: study the tendency of N + / O + ratio of escape as a function of Solar forcing N+ ?N+ ?N+ ?N+ ?

4. NITRO in-situ s/c measurements  Mass spectrometer (cold): Bern  Ion analyzers (0.001 - 40 keV): (1) Narrow mass range: Kiruna (2) Wide mass range: IRAP, Toulouse  Ion mass analyzer (> 30 keV): UNH  Electrons: MSSL  Magnetometer: Graz  Waves (Ω N ≠Ω O ): Prague  Search Coil (Ω N ≠Ω O ): LPC2E  Langmuir Probe: Brussels  ENA monitoring substorms: Berkeley  ASPOC (s/c potential control): s/c subsystem NITRO remote sensing s/c  Optical emissions: LATMOS & Japan (1) N + : 91 nm, 108 nm (2) N 2 + : 391 nm, 428 nm (3) NO + : 123-190 nm, 4.3 µm (4) O + : 83 nm, 732 / 733 nm  Mass Spectrometer: N, cold N + : GSFC  Ion analyzer (< 0.1 keV): Kiruna  Electrons: UK  Langmuir Probe: Brussels  Ionospheric optical camera: TBD  Magnetometer:  Waves (Ω N ≠ Ω O ): Prague  Search Coil (Ω N ≠ Ω O ): LPC2E Orléans  Ion analyzer (< 50 keV): Japan North South In-situ s/c: Spinning ~800 km x 6 R E i ~ 69° Remote-sensing s/c: 3-axis stabilised H ~500 x 2000 km Ring Current N+N+ N+N+ N+N+ N+N+ Upwelling: ~10 eV Injected ~10 keV N+N+ Upwelling: ~10 eV

5. Small Mission proposal submitted to ESA: 2012 PI: M. Yamauchi, Co-PI: I. Dandouras “Quad Chart” submitted to NASA (Heliophysics): January 2013 LOI for an M4 mission proposal submitted to ESA: September 2014 Need for a “Nitrogen” mission Understanding Nitrogen distribution around Earth and its escape mechanisms. The N / O ratio differs strongly between the “sister planets”. Nitrogen is a key-element for biomolecules. There are no N + / O + ratio observations in the ~0.05 - 30 keV domain