Transcript 2. Why N/O ratio @ Mars

Nitrogen Ion TRacing
Observatory (NITRO) for
ESA's M-class call
M. Yamauchi, I. Dandouras, H. Rème, P. Rathsman,
and NITRO proposal team.
IRF (Kiruna, Sweden), IRAP (Toulouse, France), OHB-Sweden (Kista, Sweden), NASA/GSFC
(USA), UNH (Durham, USA), LATMOS/IPSL (Guyancourt, France), U. Bern (Switzerland),
UCL/MSSL (London, UK), IWF (Graz, Austria), IASB-BIRA (Brussels, Belgium), IAP/ASCR
(Prague, Czech), LPC2E (Orleans, France), Inst Space Sci. (Bucharest, Romania), Tohoku U.
(Sendai, Japan), IAXA/ISAS (Sagamihara, Japan), UCB/SSL (Berkeley, USA), SwRI (San
Antonio, USA), U. Athens (Greece), LPP (Paris, France), Aalto U. (Helsinki, Finland), FMI
(Helsinki, Finland), U. Tokyo (Kashiwa, Japan), SRC-PAS, (Warsaw, Poland), U Sheffield (UK),
GFZ, (Potsdam, Germany),UCLA (Los Angeles, USA), etc.
poster [email protected] (EGU2015-4104), Wednesday (2015-4-15)
NITRO for M4:
1
Primary objective: Investigate Nitrogen budget of
near-Earth space in comparison with Oxygen budget,
because the N/O ratio of escape is poorly understood
but important for:
Earth evolution / origin of life: Amino acid formation depends on
oxidation state of N (NH3 or N2 or NOx) and the relative abundance of
N, O, & H near surface. Current measurements can be used to
determine how the atmosphere evolved on geological time scales.
Planetary atmosphere: N on Mars is only 0.01% of Earth ~ Venus ~ Titan). To
understand the abundances on other planets, we first have to understand
the Earth case.
Magnetosphere: cold N+/O+ escape correlates with F10.7 & Kp. With similar M/q,
but with different ionospheric scale heights, they are good tracers to understand
ion outflow dynamics and circulation.
Exosphere and Ionosphere: Our knowledge of exosphere > 1000km is very poor,
and variability of ionospheric N+/O+ ratio is poorly understood.
Space Plasma Physics: Different V0 between M/q=14 and M/q=16 gives extra
information on plasma energization mechanisms.
NITRO for M4:
2
Nitrogen is an essential element for life
Miller’s experiment (Miller and Urey, 1959).
Pre-biotic type atmosphere + discharges
 formation of amino-acids !
The result depends on the oxydation 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 !)
NITRO for M4:
3
Open questions on Nitrogen
1. N/O ratio @ ancient Earth?
2. Why N/O ratio @ Mars <<
@ the Earth, Venus, Titan
N < 0.01% of
Earth/Venus
rich in N
Venus
Earth
exist
Mars comet
NITRO for M4:
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Our knowledge on Earth’s N+ behavior is poor
(a) Dependence on geomagnetic activities is larger for N+ than O+ for both <25 eV
(Yau et al., 1993) and > 30 keV (Hamilton et al., 1988).
(b) N+/O+ ratio varies from <0.1 (quiet time) to ≈ 1 (large storm). What we call O+ is a
mixture of N+ and O+. This also applies to O++.
(c) [CNO group]+ at <10 keV range is abundant in the magnetosphere.
(d) Ionization altitude of N (eventually N2) is likely higher than for O in the ionosphere
(when O+ is starting to be heated, majority of N is still neutral).
(e) N/O ratio at Mars (and C/O ratio at Moon) are extremely low compared to the other
planets.
(f) Molecular N2 was detected even Martian soil and comet (Rosetta).
(g) Isotope ratio (e.g., 15N/14N) is different between different planets/comets. (But
instrumentation related to this requires M/∆M > 1000, i.e., large mass, and is
outside our scope.)
One thing clear is that O+ behavior and N+
behavior are completely different!
NITRO for M4:
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What should be observed
(1) Magnetospheric density distribution for N+ and N2+, O+, H+, He+, and He++.
- Average 3D magnetospheric distribution and its orbit-to-orbit variation
- Spatial and temporal variability of imaged line-of-site column density
(2) Energy distribution of each species in the magnetosphere.
- Energy distribution (degree of energization and its direction)
- Time delay between direct low-energy filling and convective high-energy filling
(3) Neutral density and ion flux in the upper exosphere/ionosphere > 1500 km
- Average altitude distribution
- Spatial and temporal variability
- Relation between the ionospheric/exospheric density and magnetospheric density/energy:
(4) Quantities that significantly controls the ion energization and escape
- Correlation between wave and ion velocity distributions of N and O in the magnetosphere
(5) Extra measurements that take advantage of basic spacecraft configuration
- Correlation between wave and ion velocity distributions of N and O in the ionosphere:
- Relation between sunward return flow and ion dynamics in the magnetosphere.
- Heavy ion precipitation flux above the ionosphere.
NITRO for M4:
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Possible methods of separating N+ & O+
(1) In-situ method
Mass Spectrometer (cold): high M/∆M
Mass Spectrometer (energetic): high M/∆M
Ion (Mass) Analyser (hot): high g-factor & marginal M/∆M is improving
— Magnet, grid-TOF, reflection-TOF, MCP-MCP TOF, shutter-TOF, etc —
Photoelectron: exact M but it gives only connectivity from ionosphere
Wave (ΩO+≠ΩN+): a challenge because of ∆f/f  ∆M/M < 7%
(2) Remote sensing of emission (line-of-sight integration) from above the
ionosphere (>1800 km) & outside the radiation belt (>60° inv)
N+ (91nm, 108nm), N2+ (391nm, 428nm), NO+ (4.3 µm), NO+ (123-190nm=weak),
O+ (83nm, 732/733 nm): exact M but must fight against contamination from
ionosphere and sensitive to radiation belt background
⇒ By combining both methods (i.e., with two spacecraft),
we have 3-D mapping of N/O in the magnetosphere NITRO for M4:
7
Unique Orbit
NITRO for M4:
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Payloads
In-situ #1 mother (spinning)
* Ion mass spectrometer (ion) (Bern)
* Ion mass analyzers (0.03 – 30 keV):
(1) Heavy ions only (Kiruna)
(2) Wide mass range (Toulouse)
* Ion mass analyzer (> 30 keV) (UNH)
* Magnetometer (Graz)
* Langmuir Probe (Brussels)
* Waves analyser (Prague)
* Search Coil (ΩN≠ΩO) (Orleans)
* Electron analyzer (London)
* Radiation belt vertual detector (Athens)
* ENA monitoring substorm (Berkeley)
Remote sensing & monitoring (3-axis)
* Optical (emission) (LATMOS & TokyoU)
(1) N+: 91 nm, 108 nm
(2) N2+: 391 nm, 428 nm
(3) O+: 83 nm
* Mass spectrometer (cold N+ and neutrals)
(Goddard)
* Ion analyzer (< 0.1 keV) (Kiruna)
* Ionospheric optical camera (Tohoku)
* Langmuir Probe (Brussels)
* Magnetometer (Graz)
* Electron analyzer (London)
* Waves analyser (Prague)
* Search Coil (ΩN≠ΩO) (Orleans)
* Ion analyzer (< 50 keV) (ISAS)
* (Potential Control=SC subsystem)
* colored: nominal, * black: optional
NITRO for M4:
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Mass coverage
NITRO for M4: 10
Summary
With an unique orbital configuration and recently developed
reliable instrumentation, NITRO can target nitrogen’s 3-D
dynamics for the first time in the Earth’s magnetosphere.
This is the first step in understanding of the evolution
"planet Earth", which is a mandatory knowledge in
estimating the ancient Earth's chemical condition for aminoacid formation (Astrobiology), as well as the nitrogen
differences between the terrestrial planets (Planetology).
The required instrumentation can also reveal key questions
on Magnetospheric, Ionospheric, Exospheric dynamics and
basic Space Plasma Physics.
NITRO for M4: 11
Spectra line (Å)
Hot ion (lab calibration)
Cold ion (lab calibration)
NITRO for M4: 12
Remote sensing SC
In-situ SC
NITRO for M4: 13