The topics discussed include the following: the dynamic atmosphere of Mars; possible similarities with Earth and Venus; the atmosphere and ionosphere of Mars; solar wind interactions; future approved missions; and possible future mission

Brace, Larry H.

English

NASA Technical Reports Server

N93-26893
The Upper Atmosphere and Ionosphere of Mars
Larry H. Brace
Space Physics Research Laboratory
The University of Michigan
Ann Arbor, M148109.
Presented at the Workshop on Electrical ,and Chemical Interactions of Mars.
November, 19-20, 1991
Lewis Research Center, Cleveland, Ohio.
SUMMARY
TheDynamic Atmosphere of Mars
The Martian atmosphere is believed to be highly variable and dynamic, much more
so than the atmosphere of Earth. Figure 1 illustrates certain aspects of this dynamic
behavior. High winds blowing over high relief surface features produce density
variations, usually identified as gravity waves, having peak to peak amplitudes of 15
to 20%, as is evident from the Viking 1 and 2 Lander measurements shown in
Figure 2. These structures grow as they propagate upward into the thermosphere and
ionosphere (>80 km) where they deposit energy and momentum that should
drastically affect the thermal and chemical structure of Low Mars Orbital (LMO)
environment; i.e, the region between about 100 and 400 km.
Possible Similarities with Earth and Venus
The upper atmospheres of the terrestrial planets are all known to be highly dynamic.
Knowledge of this behavior at Mars is very meager, but the upper atmospheres of
the other two (Earth and Venus) have been rather thoroughly measured. Earth
satellites like the Atmosphere Explorers 1 have shown that upper atmosphere density
disturbances are most prevalent at high latitudes (Figure 3). At Venus, the Pioneer
Venus Orbiter2 Neutral Mass Spectrometer has shown that high amplitude gravity
wave structure is common at the terminators, and that this behavior is not associated
with any particular surface features (Figures 4 and 5). Many Space Shuttle flights
carrying sensitive accelerometers have measured similar features between 60 and 160
km during reentry (Figures 6). A new Earth upper atmospheres mission, called
TIMED3, is now being planned to study more carefully the coupling between the
upper atmosphere and the thermosphere/ionosphere. The comparable regions at Mars
have yet to be explored globally.
25
https://ntrs.nasa.gov/search.jsp?R=19930017204 2020-03-17T05:42:00+00:00Z
The Atmosphere and Ionosphere of Mars
Much more is known about the lower and middle atmosphere of Mars than about its
upper atmosphere, including the thermosphere and exosphere. More is known about
the electron density in the ionosphere, since that parameter can be measured by radio
occultation measurements without passing into the ionosphere. Temperature profiles
of the lower atmosphere up to about 30 km were obtained in 1970 and 1971 by the
Mariner 9 IR limbscanning experiment 4, and radio occultation measurements of the
ionosphere provided hundreds of electron density vs height profiles of the
ionosphere between about 100 "lan and 400 km5 (Figure 7). A striking result was the
great orbit to orbit variability of the altitude of the ionospheric peak (Figure 8), a
result that is believed to reflect the great variability of thermospheric density that is
to be expected from the variability seen at lower altitudes.
Solar Wind Interactions
The Phobos-2 spacecraft did not penetrate the ionosphere or thermosphere of Mars
(periapsis N 870 km), but did perform many valuable measurements7 that shed light
on the nature of solar wind interactions with the planet and on its energetic particle
environment at its circular orbit altitude of about 6000 km. Figure 9 is a cartoon
showing the suspected escape of O + ions down the Martian tail as a result of solar
wind interactions. Figure 10 shows the measurements of the energetic O + ion fluxes
measured some 6000 km down the tail, apparently escaping the planet. These
energetic ions represent part of the energetic particle environment to be expected in
Mars orbit.
Future Approved Missions
?
Mars Observer is expected in 1993 to extend the gas temperature measurements to
somewhat higher altitudes than those achieved by Marine? 9 limbscanning, but its
sun-synchronous orbit will provide measurements at 0nly two opposing local times
(02 and 14 hrs). MO will leave the thermosphere largely unexplored, since it will
have no related in situ measurements, but it will obtain additional electron density .
profiles via radio occultation. The Soviet Mars-94 mission provides the only hope of
Ieaming more about the composition and temperature of the Martian ionosphere, but
its perigee altitude (>300 km) will probably only an occasionally dip into the upper
ionosphere, and this will not be low enough to permit in situ measurements of the
thermosphere itself. A topside sounder should provide additional electron density
profiles down to the altitude of the peak density.
Possible Future Mission
Past missions, and the missions now being implemented will have left unaddressed
most of the important questions about the nature of the LMO environment. The
global variations of thermospheric ,and ionospheric composition and temperature will
26 N
E
R
remain unknown. The temporal variations of the density, temperature, composition
and winds in the thermosphere and ionosphere (local time, seasonal, solar cycle,
response to local and global dust storms) remain almost totally unknown. Nor are
the amplitudes and scale sizes of smaller scale structures (such as gravity waves)
known for the upper atmosphere and thermosphere. Viking 1 and 2 confirmed their
existence but their global distribution, local time distribution, and frequency of
occurence is completely unknown. The martian contribution to the energetic particle
environment in LMO is also almost compietely unknown.
As for new missions that will help cure our ignorance of the LMO environment,
none are currently approved. A long advocated Mars Aeronomy Orbiter8 has been
proposed to study this region. In its initial elliptical orbit phase, it would be a deep
diver capable of making both in situ measurement of the height variations down to
the vicinity of 120-130 kilometers and remote measurements of the middle and lower
atmosphere, including dust. Figure 11 shows a low passage of MAO through such a
wave train The path of an entry probe which could be deployed from such a satellite
is also shown traversing the same wave train at lower altitudes. Such measurements
will also reveal the amplitude of the density enhancements that are believed to
accompany local or global dust storms. Figure 12 illustrates an MAO and entry
probe traversal of a region perturbed by an underlying local dust storm. Figure 13
shows the Strawman payload recommended for MAO to make such measurements.
Later in the MAO mission, aerobraking maneuvers will be used to circularize the
orbit to provide a more global view of the atmosphere, ionosphere, and particles and
fields environment at altitudes above about 130 km. Ion and neutral mass
spectrometers and various cold plasma probes would measure the altitudinal and
global variations in the ionosphere and thermosphere, as well as define the amplitude
and scale sizes of the gravity wave structures. They will also be able to determine
whether such structures are associated with specific surface features or are locked
into a diurnal pattern, as found at Venus 2. MAO fields and particles instruments
would illucidate the role of solar wind interactions as a source of energy and
dynamics of the ionosphere and thermosphere and the importance of atmospheric
escape in the continuing evolution of the Martian atmosphere.
The MAO mission, while essentially focused on scientific questions about planetary
atmosphere processes, will have important spinoffs for future manned and robotic
explorations of the planet 9. It will define the atmospheric drag environment to be
encountered in LMO. It will identify the most dynamic atmospheric regions that
perhaps should be avoided when selecting potential targets for aerobraking or
aerocapture maneuvers. It will add to our meager kno_vledge of the energetic particle
environment in LMO.
27
Specific MAO Spinoffs for Knowledge of the LMO Environment
Chemical erosion of s/c surfaces: Define the spatial and temporal variations of
atomic oxygen, the major constituent above
about 200 kin.
Electrical design of spacecraft: Define the ionospheric medium to evaluate
the need for isolation of future s/c power
systems from tlae conducting plasma to avoid
unnecessary s/c charging and leakage
currents.
Orbital lifetimes:
Aerobraking and Aerocapture:
Impact Ionization Effects
Define the atmospheric densities and their
variations to permit accurate orbital lifetime
predictions and propulsion requirements to
offset drag effects.
Identify dynamic regions of the Martian
atmosphere that should be avoided as
aerocapture targets to assure a safer,
smoother ride and a more predictable initial
orbit.
Measure the electrons, ions, and airglow
produced by the spacecraft as it dives deeply
into the lower thermosphere (-100-130 km).
28
i
References
C. A. Reber, A. E. Hedin, D. T. Pelz, W. E. Potter, and L. H. Brace, "Phase
and Amplitude Relationships of Wave Structure Observed in the Lower
Thermosphere", J, Geophys. Res., Vol.80, No. 34, 4576-80, 1975.
2. W.T. Kasprzak, A. E. Hedin, H. G. Mayr, and H. B. Niemann, "Wavelike
Perturbations Observed in the Neutral Thermosphere of Venus", Geophys. Res.
Letts.,7, 106, 1988.
3. Timed Science Definition Team, "Thermosphere-Ionosphere-Mesosphere
Energetics and Dynamics, (TIMED)", a Pre'phase A Study, A report of the SDT,
July 1991.
4. Conrath, B. J., "Thermal Structure of the Martian Atmosphere During the
Dissipation of the Dust Storms of i97i", Icarus, 24, 36-46, 1975.
5. Kliore, A. J., D. L. Cain, G. Fjeldbo, B. L. Seidel, M. J. Sykes, and W. I.
Rasool, "The Atmosphere of Mars from Mariner 9 Radio Occulation
Meassurements", Icarus, 17, 484, 1972.
6. Seiff,A., and D. B. Kirk, "Structure of the Atmosphere of Mars in the Summer
at Mid-latitudes", J. Geophys. Res., 82, 4364, 1977.
7. Lundin, R., A. Zakharov, R, Pellinen, S. Barabasj, H. Borg, E. M. Dubinin, B.
Hultqvist, H. Koskinen, I. Liede, and N. Pissarenko, "ASPERA/PHOBOS
Measurements of the Ion Outflow from the Martian Ionosphere", Geophys. Res.
Lett., 17, 877, 1990.
o Hunten, D.M, et. al. "Mars Aeronomy Observer. Report of the Science Workidg
Team", NASA Technical Memorandum 89202, Jet Propulsion Laboratory,
Pasadena, Calif., October, 1986.
o Larry H. Brace, "An Aeronomy Mission to Investigate the Entry and Orbiter
Environment of Mars", Amer. Astronautical Society, The Case for Mars l/l:
Strategies for Exploration, Vol. 74, Science and Technology Series, pages 245-
257, 1989.
10. Zhang et al., "A Post-Pioneer Venus Reassessment of the Martian Dayside
Ionosphere as Observed by Radio Occultation Methods," J. Geophys. Res.,
95, No. 89, 14,829-14,839, 1990.
11. Zhang et al., "An Observational Study of the Nightside Ionosphere of
Mars and Venus with Radio Occultation Methods," J. Geophys. Res., 95,
No. A10, 17,095-17,102, 1990.
29
Figure I.
---,.'_--- ART|
SOLAR
- _ - INTERACTIONS , SOLAR
• WIEUV
MEAN iNSOLATION
_Em_LL
STRUCTURE ?
_.oo _ 8n/AKIHO
._ _ . WAY[S;' _ rnoc[ss[$
H [M|,._-'TR y
ku y. CO * OH
\.
"'_ . ./_J-'_oanAl,tlY _ CO 2 * X
70"
40-
30"
20-
10.
0-
-20 -15 -10 -5 0 5 10 15 _0
Dense/deviat;on in percent from northern summer mean
_to_m
100'
-20 -15 -SO -5 O 5 10' ,. 15 20
Den:_/debt;on in percent from _ sunu_r moan
Figure 2.Viking 1 and 2 Lander measurements of density normalized by the
COSPAR model a_nosphere, Large waves were present at aerobraking
altitudes. This is the only hard information we have about the wave structure
at these altitudes. (from Environment of Mars. 1988)
30
m
i
B
|
A cartoon showing the dynamic atmospheric processes that would be invest
igated by the Mars Aeronomy Orbiter. (from the MAO Science Team
Report, NASA Tech. Memo 89202).
He;_t (i_) 4 "r_0'50; _ ki-__ itudcs
z
All 8 FEO1974
fl
_0.20r
-_o.
•_O.lOr f_ p
I
I_T. G3" 60"
ALT. 300 250
05'32 UT LOIIC;ITUOE109°
Figure 3.
400 km
---4 F---
"\.
rV_
_tj
25 km
----0-..--
__i I A_o_
! I
55" 50" 42" 34' 29" : 22" 17"
200 175 158 |15 200 250 300 km
Density variations (upper panel) in the Earth's themosphere measured by
Atmosphere Explorer-C. The greatest wave amplitudes are found at higher
latitudes where auroral energetic particles heat the atmosphere.
C.A. Reber et al., J. Geophys. Res., Vol. 80, No. 34, 4576-80, 1975, copyright
Geophysical Union.
by the American
31
1010 i , , ' ..j,l_,V.A.,.r,._._.' ' ' ' He X O.2O0ORB,T474 ,f ! 17" . x ._ooo
- /i i ', I\ o
109 I 71, "
#. ._. l iv.ll _ CO X 8.000
, .f, -, .,d_, '_ \ ,-, co, x zooo
-..- , "4_ /Lie' ' t"_ ' N2
t:: • ! I./W I Wi I_ (::0
u) I ,_ I P,I
,z lo _, I Jr , i'__
:brat ; I !%N
106 _._q_l , ! I ,
_l I -, _,+ l* !
4" 4 n4_
qp_
10 5 .... ]: i ! ,.... , :, ...... n........ , ....... , ............. _
,,_ ,_: ,_ :-,. -1oo:_,. 0 = :lOO ,. _ 2. ,_ I
ALT 373.7 296.9 236.3 192.4 165.9 157.1 165.9 192.4 236.3 296.5 373.7 KM
LST iU IS,4 IS_ la.S lS:_ le.S le.$ iu is.o lS.1 ls_ HR
--145.0 --146'7 --148.3 --145.7 --151.1 -152.4 -153.7 --154J --156.1 --15"72 -158.4 DEG
I0 , ' ', , ; ',' , , , ,
-.._- He X 0.2OO
ORBIT 180
,jr"'- ""_ N X 1.000
1. 9 .,_ _ 0 X 8.000
,v j_," __#'O_'_ "_ N z X 10.000
..-. .f ,,_ ,',% % co x 1.ooo
I _ _ _. "_ CO 2 X 0.250
;;
10 CO
10 6 l . , o .
% C02
_¢- ..... -.,, 7+.'.'g+ °
,p
105 J , i i , i i n ,
-250 -2_ -tso -lOO -so o so lOO 1_ 20o _ sEc
ALT 387.8 311.4 251.0 207.4 181.0 172.2 181.0 207.4 251.0 311.4 387.8 KM
LST 10.7 10.8 10.9 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 HR
SZA 39.8 35.5 31.4 27.1 22.7 llLS 14.4 10.7 7.8 5.8 8.3 DEG
CLAT 38.4 34.5 30.3 26.1 21.9 17.6 13,3 9.0 4.7 0.5 -3.6 DEG
CLON --144.0 -145.8 --147.6 -145.2 --150.7 -152.1 -153.5 -154.8 -156.1 -157.3 -158.5 DEG
Figure 4 Plot of ambient density versus tim¢ from periapsis for He, N, O, N z, CO, and co z measured on orbits (horror
180, near noon, and (top} 474, near the terminator. The densities have been sealed by the factors shown. Atomle nltrog(
was not routinely measured prior to orbit 190. The points below the main data line in orbit 180 for O, N 2, CO, and C(
are due to a partial shadowing of the ion source by the spacecraft antenna at extreme angles of attack.
W.T. K_przak el; al., Ceophys. Res. Letts., 7, 106, 1988, copyright by the American
Geophysical Union.
32
0.4
_ o3
O
_ O.Z
0.1
.0.0
0.5
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g 0.3
o
0.2
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o
_ o_
Ig
0.1
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• _ • i • t , i , i • ! , i , i • i o i = ! •
__a:$PECIES: CO_
• _ • J o _ • i , a._, i , i • i • d , _ , ¢ • .
_,o,n, " : , _o,_o,o,o._
• i , i • i , ! o i , ! • ! • i i i _ i • ! , :,.
SPECIES: He
2 4 6 8 10 t2 14 16 19 20 22 24
LOCAL SOLAR TIME IN)
'' .... ;;c,'.::,.....
• | • [ . | • i , i , i ! | ! i • i • I • | •
SPECIES; N
2 -4 6 8 10 12 t4 16 18 20 22 24
LOCAL SOLAR TIME t)u|
--o.,.,- I00%
90%
75%
50%
25%
• AVERAGE
O AVG ERR
Figure 5. The statistical amplitudes of density waves in the Venus thermosphere shows
that the atmosphere is most dynamic near dawn and dusk, and on the night-
side in general. The dayside is quite smooth. Similar information is not
available for Mars.
W.T. Kasprzak et al., Geophys. Res. Letts., 7, 106, 1988, copyright by the American
Geophysical Union.
33
I.Sr
1.4
Figure 6. The ratio of the atmospheric density (13) to a 1978
model density based on STS-13 and 6 accelerometer
measurements. These measurements reveal large amplitude
gravity wave structure at aerobraking altitudes in the Earth's
upper atmosphere.
MARINER 9 REVS 22-28 ENTRY
500
-I
'=" 4oo 53 52 52 52 52 52 51 SZA
_300
1,--
,_ 200
100
3 4 5 5 5 5 5 5 5 5
LOG ELECTRON DENSITY (cm-3)
Figure 7. Examples of altitude profiles of
dayside ionospheric electron density at Mars,
derived from the radio occultation experi-
ment on Mariner 9 [from 7_Jumg et at,
1990a]. SZA is the solar zenith angle at
which the profile was obtained (subsolar is
SZA = 0; SZA = 90 is the terminator).
Zhang et ai., J. Geophys. Res., 95, No. 89, 14,829-14,839, 1990, copyright by the American
Geophysical Union.
34
i
=
=
=
=
i
=
7_
m
!
=
=
!
!
m|
i
=.
Figure 8. Plots of the density (bottom) and
amtuae trap) of the peaks in the elecla'on
density profiles observed at Mars as a
function of solar zenith angle (adapted from
Zhang et al. [1990b]).
E2oo /
I
1.00 ]
_: 125
I.d
IX.
40
200
E
¢,)
c_.150
F IO0
u'i
"7
LIJ
t'-, 50
"<C
IJJ
o_ °4o
Zhang et al., J. Geophys. Res., 95, No A10,
Geophysical Union.
Mars Ionosphere Peaks
+ _. +
+
+,* "._..+
"l" lm
Ill I• •
:.I.._._
el •
6'0 8'o
! ....
60
SOLAR
• : "•;,o° •
_'_'__" "_, _= ;...__%'__.i
80 100 120
ZENITH ANGLE, deg
L: .
17,095-17,102, 1990, copyright by the American
140
140
Solar
Wind _>
Iono-c
Figure 9. A cartoon illustrating the escape of energetic O+ ions
from Mars, based on Phobos 2 measurements such as those
shown in Figure 10.
35
PHOBOS / ASPERA 4 - 5 February 1989
Lundin
Union.
1000,
100
10
e_
0.1
1Q
1
_ 0.1
I 0.1
..... :E l-.... v:/-'u _-"-t- ......... -I...................
IIMP MPMLB
• ! I I a m |* ! , : _ : . _, _,. ;.,
I
. • t l , _ I ,
| | l
UT 23:00 01:00 03:00 05:00 07:00 09:00
RCkm)12206 8466 21288 30927 :38794 45473
Figure ]0. ASPE_ measurements from Phobos2 Showing
energetic ions escapL_g down the Martian tail. These ions
contribute to the energetic particle environment to be encountered
in Mars orbit.
et al., Geophys. Res. Letts., 17, 877, 1990, copyright by the American Geophysical
36
m
S
180 km -
130 km -
70
30 km -
Atmospheric Gravity
Winds
Martian Surface
Figure 11. The trajectory of MAO, and an entry probe, tlu-ough a
series of gravity waves propagating upward out of the Martian
lower atmosphere.
Orbiter
nt_ry
robe
180 km -
130 km -
70 km-
Upwelllng atmosphere
Entry
30 km- Local Dust Storm
' Martian Surface
i
Figure i 2. The trajectory of MAO, and an entry probe, through
the upwelling atmosphere produced by heating associated with a
local dust storm at Mars.
37
TABLE V.1 MAO SWT REDED INSTR_
MASS POWER TELEMETRy1
OORE PAYLOAD
Neutral Mass Spectrcmeter 2 (NMS) I0.0
Fabry-Perot Interferometer (FPI) 13.5
UV + IR Spectrometer (UV + iRS) 5.0
Ion Mass Spectrometer (IMS) 2.5
Netarding Potential Analyzer + Ion
Driftmeter (RPA + IEM) 4.5
Langmui r Probe (STP) 2.0
Plasma + Energetic Particle
Analyzer (PSPA) 10.0
Magnet_ter (MAG) 3.0
Plam_a Wave Analyzer (PWA) 5.5
Radio Science 3 (RS) 4.5
SECO_Y PAYlfIAD
8.5 180
5.5 30
7.0 130
1.5 60
4.o 80
4.0 3O
9.0 320
3.5 200
3.5 130
12.54
60.5 kg 59.0 W 1160 bps
Infrared Atmospheric Sounder (IAS) 8.0
UV + Visual Synoptic Imager (UV + VSI) 9.0
Neutral Winds/Temperature (NWTS)
Spectrometer I0.0
7.5 260
8.0 i000
9.0 180
27.0 kg 24.5 W 1440 bps
TOTAL 87.5 kg 83.5 W 2600 bps
1 Individual instrument rates can _ highly variable and will depend upon
the final payload and orbit seiec£ion. The rates listed are based
upon typical duty cycles for_each experiment and they have been
averaged over the orbit (i.e., 6,000 x 150 km orbit has been assumed).
Includes limited wind measuring capability.
Consists of S-band transponder and stable oscillator.
i0 W (continuous) for the stable oscillator and 25 W (10% duty cycle)
for the S-band transponder.' •
Figure 13. The MAO Recommended Instrument Payload (from
the MAO Pre Phase A Study)
2
3
4
38


The upper atmosphere and ionosphere of Mars

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