M. Yamauchi (IRF, Kiruna),

I. Dandouras (IRAP, Toulouse),

and the NITRO proposal team

4th SERENA – HEWG Meeting, Key Largo, May 2013

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

in Nitrogen

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!)

(A) Nitrogen as essential element of life

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)

(B) N 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

(B) N and O in the brother plants

MarsVenus Earthrich in N

N < 0.01% of Earth/Venus

Nitrogen (N/O ratio) Mystery

N/O ratio at Mars << at the Earth, Venus, Titan

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.

(B) N in the brother plants

It is not easy to estimate the “value” of ancient abundance.

However, tendency of N/O ratio of escape against solar forcing might be easier to obtain ( see example).

How about observation of escape?

Example: guessing O+/H+ ratio

H+< 50 eV O+< 50 eV

High UV

Low UV

Akebono/SMS(Cully et al., 2003)

H+> 10 eV O+> 10 eVion escape

Polar/TIMAS(Peterson, 2002)

Type Mechanism Explanationthermal, neutral

Jeans escape + momentum exchange

Thermal tail exceeds the escape velocity + Escaping light molecules collide with heavier molecules.

thermal, neutral/ion

Hydrodynamic blow off Same as the solar wind formation mechanism (extreme EUV radiation during early Sun).

thermo-chemical, neutral/ion

Photochemical heating Release of e.g., recombination energy of the excited state accelerate the atom.

thermal & non-thermal, ion

Ion pickup + secondary sputtering of neutrals

Ions that are newly exposed to solar wind are removed by the solar wind ExB.

non-thermal, ion

Ion energisation by EM waves and E//

EM disturbances and static E energize ions by, e.g., the ion cyclotron resonance.

non-thermal, ion

Large-scale momentum transfer

The solar wind dynamic pressure and EM forces push the planetary plasma anti-sunward at the boundary region, by e.g., mass-loading, instability, and reconnection

Escape mechanisms

Dependence on the solar forcingHigh UV flux of early Sun expansion of the ionosphere beyond the magnetopause. Treat as non-magnetized planet

Ancient

Ancient?

Quick rotation of early Sun stronger dynamo stronger solar maxium stronger CME

Increase in FUV (or T) Psw Bsun MeV e- Pick-up (important)

++ ++ + (unchanged?)

Non-thermal heating

(++?) ++ ++ +++

Jeans & photo-chemical

+++ for H+ unchanged unchanged (+?)

O+/H+ ratio of escape

?? (+++?) (+?) (++?)

N+/O+ ratio of escape

(?) (?) (?) (++?)

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

Increase in FUV (or T) Psw Bsun MeV e- Pick-up (small) unchanged (+?) unchanged unchangedNon-thermal heating

+++ +++ ++ (+?)

Jeans & photo-chemical

+++ for H+ unchanged unchanged (+?)

O+/H+ ratio of escape

?? +++ ++ (++?)

N+/O+ ratio of escape

(+?) (+?) (?) (++?)

Guessing escape (Magnetised)

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

Present knowledge on N+ escape(1) Akebono (1989 launch): cold ions < 0.05 keV

N+ N+

// direction to B ram direction = ambient plasma

N++ N++

Present knowledge on N+ escapeMore drastic change of N+ than O+ for < 0.05 keV

But destination and acceleration is not clear

N+ N+N2

+

Present knowledge on N+ escape(2) AMPTE (1984 launch): energetic ions > 30 keV

(Hamilton et al., 1988)

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.

Technology is within reach!

MEX / IMA, IRF

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.

Technology is within reach!

P. Devoto, J.-L.Médale, and J.-A. Sauvaud, Rev. Sci. Instru., 2008

Beam energy of 10 keV

CESR/IRAP Time-of-Flight R&D: Grazing-incidence MCP as “start foil”

(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.

Need for a mission

Mission orbit and PayloadNorth

South

In-situ obs.

ImagingAll types of ion mass

analysers:

(1) Magnet

(2) Grazing-incidence

MCP as “start foil”

(3) Shutter TOF

(4) Reflection TOF

(various types)

ENA of 1-10 keV

(substorm injections)

Optical (emission)

(1) N+ : 91nm, 108nm

(2) N2+ : 391 nm, 428nm

(3) NO+

cf. Auroral N2+ emission

e- collisions ionise N2 to make exited N2

+ that emits blue line (but N2 is exited or even N2

+ pre-exists by solar UV during equinox)

Spin-offs of N & O observations

Qualitative differences between O+ & N+

(1) Transport: Magnetospheric Physics

H+

O+

How about N+ and N2+?

In-situ Payload Requirements

Science Question What and where to measure?

requirement

N+ escape history vs O+ or H+

N+, O+ and H+ at different solar and magnetospheric conditions.

#1, ∆t<1min

Ion filling route to the inner magnetosphere

same as above. #1, ∆t<1min

N-O difference in energy re-distribution in the ionosphere

N+, O+, H+, J//, and e- at different solar conditions.

#1, keV e-, J//, eV ions

Ion energisation mechanisms

energy difference among N+, O+ and H+ at different altitudes

#1, ∆t<1min

#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%).

Nitrogen is an essential element of lifeN/O ratio is quite different between brother plantsNo 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.

Nitrogen is our future

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.

N/O ratio at Mars << at the Earth, Venus, Titan: We Need a Nitrogen mission