Mars - The Mystery Unfolds

208 Pages·2001·40.992 MB·English

by  Peter Cattermole

MARS
Peter Cattermole
»
ake ofa flood ofnew data and images from sev-
xploratorymissions,ourfascinationwithMarsiseven
moreintensethanitwasahundredyearsagowhenPercival
Lowellbelievedhehadobservedcanalsconstructedbylive
Martians. Although these never existed, there is evidence
that Mars once did have rivers offlowing water, shallow
lakes,glaciers,activevolcanoesofimmensesize,andexten-
sive flooding. Unlike now, in the very early days of the
SolarSystem,Marsmayhavebeenhosttothedevelopment
of primitive life. Mars: the mystery unfolds captures the
senseofcontinuingexcitementaboutMarsanditshistory
inaclearlywrittenandfullyillustratedaccountofcurrent
understanding ofthe red planet. Drawing extensively on
thewealthofresearchpublicationsinprint,itprovidesthe
readerwithan accessible treatment to satisfy the appetite
forclearscientificexplanationandspectacularimages.
This new book builds on the foundation provided by
theauthor'swellreceivedMars:thestoryoftheredplanet
(1992). Atthat time, although a large data archive existed
and an overall picture of the geological development of
Mars hadbeen painted, mainly on thebasis ofthe Viking
and Mariner 9 missions, large gaps in our knowledge
remained; for instance, relatively little was known ofthe
planet's volatile history and inventory, of the short-term
changes inclimateandweather, and ofthepossibleexist-
ence of large bodies of standing water on its surface;
and the discovery of possible organic remains in mete-
orites of Martian provenance was completely unantici- OCD
pated. Since thattime, therehasbeen muchnewresearch C—O
CD
on the old Mariner 9 and Viking archives. The large Sn?
^o ^
published output fromthe Mars Surface and Atmosphere
§^°
Through Time programme was just one example, which CD-cIrD
has enhanced ourunderstanding ofMars' volatile history CD
andestablished acknowledgementofthepastexistenceof fg>~£
palaeolakesandoceansinthenorthernhemisphere.There OC^T
have also been new programmes of Earth-based spectro- r~\o J
CD 55
scopic and infraredmeasurements, laboratory experimen- cx JO
tation,intensiveanalysisofAntarcticmeteoritesand,very 3>
recently, observations fromtheamazingHubblespacetel- J<D
escope that have rapidlychanged ourperception ofMars'
climate and daily weather patterns* providing valuable
information before the more recent arrival ofMars Path-
finderandMarsGlobal Surveyor.
Mars Pathfinder was hugely successful, providing an
immenseamountofvisual,geochemicalandphysicaldata
concerningtherocks,landscapeandweatheratthemouth
ofthehugeAresVallischannelsystem.Forthefirsttimein
nearly 30 years, thereis newfirst-hand information about
Martianmaterials.Thefirstpebblyandstratifiedrockswere
observed,aswereandesites,andstylesofrockweathering
were analyzed for the first time. As ifnot to be upstaged,
MarsGlobalSurveyorsurprisedusbyrecordingMars'very
weakmagnetic field and subsequently provided the plan-
etary community with avast new data archive that offers
usmoreandhigher-resolutionimagesofMarsthanweyet
haveofmuchoftheEarth.
. . . /continuedonbackflap
•
Digitized by the Internet Archive
2012
in
http://archive.org/details/marsmysteryunfolOOcatt
Mars
THE MYSTERY UNFOLDS
Peter John Cattermole
OXFORD
University Press
2001
Oxford UniversityPress
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Berlin Ibadan
Copyright©PeterJohnCattermole 2001
Published intheUnited States ofAmericaby
OxfordUniversityPress,Inc.
198 MadisonAvenue,NewYork,N.Y. 10016
http //www.oup-usa.org
:
OxfordisaregisteredtrademarkofOxfordUniversityPress
Allrightsreserved.Nopartofthispublicationmayberepro-
duced, stored in aretrieval system, or transmitted, in any
form orbyanymeans, electronic, mechanical, photocopy-
ing,recording, orotherwise,withoutpriorwrittenpermis-
sion ofOxfordUniversityPress.
Firstpublished in 2001 by
TerraPublishing,POBox315, Harpenden, AL5 2ZD,
England
E-mail: [email protected]
Website: http://www.rjpc.demon.co.uk
LibraryofCongressCataloging-in-PublicationData
Cattermole,PeterJohn
Mars: themysteryunfolds/PeterCattermole
p. cm.
Includesbibliographicalreferencesand index
ISBN 0-19-521726-8
1.Mars (Planet) I. Title.
QB641.C369 2001
523.43—dc21 00-047866
Printed andboundby Butler& Tanner Limited,
Frome, England
n
Contents
Preface v 5 Mars and volatiles 41
Volatile distribution amongthe innerplanets 41
Modern water found on Mars? vi
Isotopic datarelevant to Martian volatiles 42
Surficial evidence for subsurface volatiles 44
1 Mars in the Solar System 1 Palaeolakes and oceans 45
Dimensions and mass 2 Ancientglaciers? 46
The Martian seasons 3 Martian volatiles and nature ofreservoirs 46
The pattern ofdiscovery 3
Albedo markings 4 6 The ancient cratered terrain 48
The crateringrecord 48
2 Exploration ofthe red planet 6 Martian impactbasins 50
Mariner 9 7 Morphology ofimpact craters 52
Early Russian exploration ofMars 8 Crater ejecta morphology 53
The Viking missions 9 Nature ofthe ancient cratered crust 55
The Russian Phobos mission 10 Volcanoes ofthe cratered plateau 56
Mars Observer mission 12 Developmental history ofthe early crust 56
The Mars Pathfindermission 12
Mars Global Surveyor 15 7 The plains ofMars 58
Othermissions 16 Noachian and early Hesperian plains 59
Channels, plains and volcanism 61
3 The present face ofMars 18 Hesperian flow plains 61
The topography ofMars 18 The Medusae Fossae plains 62
Physiographic provinces 20 Tempe Terra plains province 63
Thermal inertia mapping measurements 23 Plains deposits ofHellas 64
Earth-based and orbiterspectral observations 25 The northern plains 65
The Martian surface layer 26
Hubble space telescope observations 27 8 Volcanism on Mars 70
Martian stratigraphy 28 Types ofvolcanic structure 72
Controls on volcanic processes on Mars 73
4 Atmosphere, weather and climate 29 Highland paterae ofthe Hellas region 73
The composition ofthe atmosphere 29 Peneus and Amphitrites Paterae 74
Pressure and temperature variations 30 HadriacaPatera 75
MarsPathfinder data 31 TyrrhenaPatera 75
MGS thermospheric measurements 34 Volcano morphology and early volcanism 77
Winds and atmospheric circulation pattern 35 Shieldvolcanoes ofTharsis and Elysium 78
Martian winds 36 The central volcanoes ofTharsis 78
Clouds and dust storms 37 Volcanic shields and lava plains ofElysium 88
Precessional effects and climatic change 39 Apollinaris Patera 89
Climate historv ofMars 40 Central volcanism on Mars 90
The nature ofMartianmagmas 91
Volcanoes, loading and lithospheric stresses 92
111
CONTENTS
9 Tectonics and the growth ofTharsis 93 14The interior ofMars 148
One-plate and multi-plate planets 93 The geoid, figure and gravity ofMars 148
Distribution oftectonic features onMars 94 Internal density profile 150
Coprates Rise and SouthTharsis Ridge Belt 98 Composition ofthe interior 151
Thegravity field ofMars 101 Global Surveyormagnetic-field measurements152
The evolution ofTharsis 102
15Geochemistry 154
lOValles Marineris 105 Spectral characteristics and chemistry 154
Physiography and topography 105 Pathfindersoils and fines 155
Form ofcanyon walls 107 Pathfinderrock 156
Wall retreat and landslide deposits 107 SNC meteorites 158
Tributary canyon development 109 New data and Martian differentiation 159
Canyon interior deposits 110
Volume and thickness ofcanyon deposits 110 16Phobos and Deimos 161
Layered deposits within peripheral troughs 112 Phobos 161
Origin ofthe layered interior deposits 113 Deimos 162
Chaotic material 114
History ofthe canyon system 114 17LifeonMars? 163
Early observations 163
11Fluvial activity and channels 116
Viking observations 163
Distribution ofvalleyand channel systems 116 Meteorites and possible Martian life 164
Fluvial activity and Mars' volatile history 117
Valley networks 118 18Today on Mars 166
Outflow channels 121
Wind activity on Mars 166
The Pathfinder landing site (Ares Vallis) 124
Aeolian erosional landforms 167
Ages ofthe channels 125
Depositional landforms 168
Terrestrial analogs ofoutflow channels 126
Pathfinder landing site weather conditions 170
Fretted channels 126
Plans forthe future 170
12The polar regions, ice and wind 127 Appendix 171
The polarcaps and seasonal variations 127 Model chronology 171
Physiography ofthe polarregions 127 Astronomical data 171
Seasonal behaviour ofthe polarregions 130 Websites about Mars 172
Wind and dust storms in cap behaviour 131
Laminated polar deposits 132 Bibliography 173
Spectral data forthe cap regions 134
The polarvalleys 135 Index 183
The circumpolar plains and dunefields 136
Dunefields and formation ofduneforms 136
Physiography ofmarginal polarregions 138
13The dichotomy 140
Physiography ofthe dichotomyboundary 140
Earlier explanations forthe dichotomy 141
mola dataand interpretation 142
Ancient oceans and lakes on Mars? 143
Shorelinetests along the boundary 144
The possibility ofglaciation 146
IV
Preface
isalmostadecadesinceIwroteMars-thestoryofthe the twentieth century, Percival Lowell believed he had
Itred planet. Although a large data archive existed - observedcanalsconstructedbyliveMartians.Althoughwe
mainlyderivedfromtheVikingandMariner9missions know these neverexisted, there is very real evidence that
-andafairly detailedpictureofMars'geological develop- Marsonce didhaveriversofflowingwaterandactivevol-
mentcouldbepainted,majorgapsremainedinourknowl- canoesofimmensesize,andexperiencedperiodsofexten-
edge. At that time, for instance, little was known of the siveflooding.Theremayalsohavebeenshallowlakes,huge
planet's volatile history or of the short-term changes in glaciersandprimitiveformsoflife.Marsmusthavechanged
climate and weather. The past existence oflargebodies of agreatdealsincethetimewhentheymayhavebeenripefor
standingwateronitssurfacehadbeenconsidered,butevi- thedevelopmentofprimitivelife,andliquidwaterwasable
dencewas disputed. Ourknowledgeofthe planet'stopog- to pondon thesurface. Maythestoryunfold.
raphy, gravity and surface composition was still rather
sketchy,andthequestionofpastliferemainedunanswered. Acknowledgements
Inthemeantime,themysteryhasdefinitelybeenunfold- No oneauthorcan haveatotalgrasp ofall aspects ofMars
ing.Theolddataarchivehasbeenturnedoverandover,and science,sothisbookisnomorethanmyowninterpretation
smeeantr.cheTdhefoMranreswSucrlfueasceabaonudtAtthmeopslpahneetr'es TeahrrloyudgehveTliompe- otoftahcekrneoswelaerdcgheanadnddatthaaonfkmaallntyhopsleanwehtoarsyeswcioernktisitssr.eIfewrirsehd
programme (msatt) hasgreatlyenhanced ourunderstand- toanddiscussedherein. Shouldtherebeanyerrorsormis-
ingofMars'volatilehistoryandgivenwidespreadacknowl- understandingsinmyinterpretationoftheirwork,theyare
edgementofthepastexistenceofpalaeolakesandoceanson ofcoursemyresponsibility.
the planet. New Earth-based spectroscopic and infrared Figure 4.1, 9.1, 9.9, 12.10, 12.14, 15.1a, 15.2, 15.4 and
data,laboratoryexperiments,intensiveanalysisofputative 15.7,Plates3, 10and 11,andTables4.1 and 14.1 werefirst
Martianmeteorites,andobservationsbytheamazingHubble publishedin[heJournalofGeophysicalResearch(Planets),
spacetelescope(hst).hayeallcontributedtoachangedper- copyright American Geophysical Union. Figures 3.3, 4.3,
ception ofwhat makesthered planettick. 4.6,12.3,12.9,13.3,13.4,15.1a,15.5and15.6arecopyright
HST has provided invaluable information about condi- of the journal Science. Both publications kindly granted
tionsonMarsandhowtheychange.Thispavedthewayfor permissionforreproduction. Authors'detailsareshownin
twohighlysuccessfulspacecraft,MarsPathfinderandMars therelevantcaptionandinthebibliography.
Global Surveyor. The former has provided an immense ThesuperbimageryobtainedbyavarietyofNASAspace-
ainmgouthnetroofckvsi,sualla,ndgsecoacpheemaincdalweaantdheprhyastictahledmaotuatchonocfertnh-e ctroaaftckfneaotwulreesdgperoNmAiSnAe/njtPlL/yMianlitnhisSpbaocoek.ScIiweinschesSpyesctiefimcsalfloyr
Ares Vallis channel system. Forthe firsttime innearly 30 permission to utilize the Mars Global Surveyor and Path-
years, there wasnew information about Martian materials finder images shown herein. The Viking and Mariner
thathadbeensampledonsite.Therewereseveralsurprises. images were kindly provided by NSSDC, Greenbelt, Mary-
Asifnottobeupstaged,MarsGlobalSurveyor,whileaer- land. DrBaerbel Lucchittakindly supplied hard copyand
obrakingonitsapproachtoMarsin1997,confirmedavery granted permission to reproduce Plates 10 and 11, as did
weakmagneticfield.Itthenprovided(andisstillproviding) DrKennethTanakaforPlate3;botharebasedatUSGS,Flag-
the planetary science community with a vast new data staff,Arizona.ThelatePaulDohertypreparedtheexcellent
archivethatputsusintheenviablepositionofhavingmore artwork for my earlier book, Mars - the story ofthe red
andbetterimagesofMarsthanweyethaveofmuchofEarth. planet,someofwhichisusedagainhere.
thrIotwisntohpeesenrtehceenftlomoidsgsatieosn,s,alilnocwliundginngetwheidhesats,athbaotuthatvhee forFbienaarlilnygIwwiitshhmtyoitdhiaonskynRcorgaesireJsoannesdfoofrTueprhroalPduibnlgisehxicnegl,-
red planetto come pouringin. InthisbookI have triedto lentstandards intheproduction ofthebook.
present a new perspective that, to my mind, makes Mars
evenmore excitingthanbefore. Its attractionto Earthlings PeterJohnCattermole Sheffield February 2001
hasapparentlynotwanedonejotsince,intheearlydaysof
MODERN WATER FOUND ON MARS?
Modern water found on Mars?
In June 2000, rumours arose that an article to be e.g. C02) were present ratherthan purewater, thenthe
published in Science magazine by Michael Malin and freezingpointwouldbemuchlowerandthecoldproblem
Kenneth Edgett was to present high-resolution images lessened. Othersalts mightalso be involved andwould
that pointed to the existence of modern wateron Mars. act in asimilarway.
Tostem mediafantasy, nasaquicklyorganized a press Clifford, Victor Baker (U. of Arizona) and Kenneth
conferenceto presentfacts ratherthanfiction. Tanaka (usgs; Tanaka 2000) argue that, although it is
Thefacts arethat study by Malin & Edgett (2000) of generallyheldthatMarswaswarmerandwetteronlyvery
150 high-resolution Mars Global Surveyor images earlyin itshistory,thistenetnowneeds re-examination.
returned since the beginning of January 2000 reveals For instance, it is known that precession could have
120 locations where fluid seepage and surface runoff increasedMars'obliquitytoasmuchas45=around5mil-
appear to have occurred. The features lack decay or lionyearsago.Thiswouldhaveenhancedsolarradiation
impactfeatures,indicatingthattheymustbeveryyoung. in the polar regions and on pole-facing slopes, and
Ifwater-formed, this fluid must have existed atthe sur- caused a general warming by sending part of the ice
face quite recently. locked inside the south polar cap into the atmosphere,
The specific landform grouping comprises a head increasing the greenhouse effect. Perhaps such warm-
alcove, associated channels and a depositional apron. ing melted subsurface ice?
On Earth, such ageomorphological package isconsist- Researchersareexcited,whetherwater,clathratesor
entwithfluid-mobilizedmassmovement.Alloccurrences salts are involved. It calls into question the belief that
arefoundonsteepslopes,atlatitudesabove30c mainly Mars has been cold and inactive since earlytimes.
,
in thesouthern hemisphere, wherethey are associated
with thewalls ofseveral large impactcraters, thechan-
nels Dao and Nirgal Valles, several graben and south
polarpits.Theyarenotfoundamongancientvalleynet-
works-formed ata time when Mars' climate and crust
mayhavebeenwarmer-norinvolcanicareasthatcould -j
havecirculatedhydrothermalenergy.Noraretheyfound *?S¥£".
inequatorial regions, butthatislesssurprising because %. \
protracted desiccation in these zones would have
removed any volatiles at shallow depths. At first sight, j
''
theirdiscoveryappearstodispelthenotionthatthecrust mi
in high latitudes is deeplyfrozen.
However,thereisanothertwist:justunder50percent
arefoundonsouth-facingslopes;amere20percentface 1;
north. Since 90 per cent lie south of the equator, this
means most are polefacing and receive less insolation
thanthosefacingtheequator;theyappeartobetheleast
likelysitesforthe releaseofsubsurfacevolatiles. Malin
& Edgett ingeniously get around this problem by sug-
gesting that groundwater moving towards the surface 1
became trapped behind an ice plug that was breached
>'
onlywhen groundwaterpressurewassufficientto burst
it, escape and cutthe gullies. 3
Stephen Clifford (lpi) points out that it is currently
impossible to create a near-surface aquifer on Mars,
becauseitissimplytoocold;yettheseepageappearsto
have emerged from layers at depths of a mere 150m.
Both Clifford and Michael Carr (usgs), suggest that if Youthful channels and aprons in East Gorgonum crater. MGS
clathrates(thatisicesofwaterandanothercomponent, imagePIA01038;centredat37.4°S 168.0°W.
VI