History of Mars Exploration
History of Mars Exploration
 Analyze historical and modern Mars data to develop an
evolving understanding of Mars.
 Models how scientists have historically viewed Mars.
Early Exploration
1609 - 1965
Early Exploration
Nicolaus Copernicus
 Published De revolutionibus orbium coelestium (On the
Revolutions of the Celestial Spheres) in 1543
Early Exploration
Tycho Brahe
 Observations of Mars in 1583 showed Mars could move
closer to Earth than it did to the Sun. Possible in a
heliocentric universe, but not geocentric.
Early Exploration
Ptolemaic System
Early Exploration
Tychonian System
Early Exploration
 Johannes Kepler
 Assistant to Brahe; derives first two laws of planetary motion in
1609. 1st law derived from Brahe’s observations of Mars.
Early Exploration
 Though these early observations helped scientists
accurately describe the motion of Mars in the sky, nothing
about the planet itself was known.
Mars retrograde motion. Image Credit: Tunç Tezel
Early Exploration
 Beginning with Galileo, scientists were able to observe
Mars with a new tool, the telescope.
William Herschel’s 40ft telescope, 1789.
Percival Lowell at Lowell Observatory.
Early Exploration
Galileo Galilei observed Mars in 1610
and wrote: “…unless I am deceiving
myself, I believe that I have already
seen that it is not perfectly round.”
Early Exploration
Christiaan Huygens made the first (known)
sketch of Mars in 1659; determined a
rotational period for Mars:
“The Rotation of Mars, like that of the Earth,
seems to have a period of 24 hours.”
Early Exploration
Giovanni Cassini calculated a rotational period
of 24 hrs, 40 min; may have been first to report
the southern polar cap in 1666.
Early Exploration
French author Bernard le Bovier de Fontenelle
wrote about Mars in 1686:
“Mars has nothing curious that I know of; its
days are not quite an hour longer than ours
and its year’s the value of two of ours. It’s
smaller than the Earth, it sees the Sun a little
less large and bright than we see it; in sum,
Mars isn’t worth the trouble stopping there.”
From Conversations on the Plurality of Worlds
Early Exploration
In 1783, William Herschel determined
Mars to have a diameter 0.55x Earth’s
and an obliquity of ~28°; noted the
south polar cap.
Early Exploration
Herschel also noted:
“I have often noticed occasional changes of
partial bright belts…and also a darkish one,
in a pretty high latitude… And these
alterations we can hardly ascribe to any other
cause than the variable disposition of clouds
and vapors…”
Early Exploration
Herschel concluded the inhabitants of
Mars “probably enjoy a situation in many
respects similar to ours.”
Early Exploration
• Giovanni Schiaparelli popularized the straight
lines he called canali (can mean “channels” or
“canals”). He also used fiume or “river.”
• Started a new nomenclature for Martian
features.
Early Exploration
Map of Mars by Schiaparelli, 1877
Early Exploration
Asaph Hall of the US Naval Observatory
discovered the two moons of Mars in 1877.
Moons
Deimos – 15 km (9.3 miles)
Phobos – 26.8 km (16.7 miles)
Early Exploration
• Percival Lowell misinterpreted “canali” to mean canals
(artificial); mapped 437 “canals” in 917 sketches; took the
idea of artificial canals to the grave.
• Calculated an atmospheric pressure of 85 millibars (8.5%
of Earth’s)
Lowell’s Martian canals, ca. 1900
Early Exploration
How did scientists view Mars at the beginning of
the 20th century?
Early Exploration
How did scientists view Mars at the beginning of
the 20th century?
- Earthlike?
Early Exploration
How did scientists view Mars at the beginning of
the 20th century?
- Earthlike?
- Like?
Early Exploration
 What are limitations to this type of mission and its instruments?
 What observations can you make from this data? (Please select the
relevant images and prepare to post them on your poster.)
 How would you interpret these observations?
 How would you generalize the Mars environment from these images
/ data?
 What new questions do you have about Mars?
 What type of data do you need to answer these questions?
Early Exploration
Setting aside the argument of whether or not the canals were real, astronomers
knew with certainty that the surface of Mars changed - dark and light patterns did
not remain the same over time.
Mars Map by Eugène Michel Antoniadi, 1930
Early Exploration
As telescopes improved, astronomers became confident that Mars had
a polar cap. The question remained, what was it made of?
Early Exploration
In 1947, Gerard Kuiper made the 1st positive ID of CO2 in the
atmosphere of Mars.
Early Exploration
• In 1950, the best guess* for the composition of the Martian
atmosphere was:
- 98.5% N
- 1.2% Ar
- 0.25% CO2
- <0.1% O
*Estimates from Gérard de Vaucouleurs; also calculated an atmospheric pressure of 87 millibars (8.7% Earth’s).
Early Exploration
• In 1963*, the “probable composition of the Martian
atmosphere” was believed to be:
• 72% N2
• 25% CO2
• 2% Ar
• < 0.5% O2
• Trace amounts of H2O
*Estimates from NASA Technical Document NASA-TM-X-56223, 1963; presented at the Symposium on
Extraterrestrial Biology and Organic Chemistry, Warsaw, June 3-12, 1963.
Early Exploration
“A third presence on Mars indicates a living world: vegetation. The
evidence is in the blue-green areas and the changes in their
appearance. Vegetation would present exactly the appearance
shown…. The seasonal change that sweeps over them is
metabolic; that is, it shows both growth and decay….”
- Earl C. Slipher, 1962
Image Credit: Lowell Observatory
Early Exploration
• Early exploration of Mars revealed it to be:
• Cold; temperatures at freezing or well below freezing
• Dynamic, at least regarding patterns on the surface; dust,
vegetation, or both?
• Low atmospheric pressure; clouds
• Unsure about the atmospheric composition
• Arid
• Polar cap – What is it made of?
• No canals/intelligent life
Early Exploration
How did scientists view Mars in the early
1960s?
Early Spacecraft Exploration
1965-1976
Early Spacecraft Exploration
Mariner 3 & 4
 “…these missions are being undertaken because Mars is
of physical and geological interest and offers the best
opportunity in our solar system for shedding light on the
possibility of extraterrestrial life. (They)…, however, are
not designed to provide answers to the question of life on
Mars.”
Mariner 4 Press Kit, October 29, 1964
Early Spacecraft Exploration
Mariner 4
Early Spacecraft Exploration
Mariner 4
Early Spacecraft Exploration
Mariner 4
 Notable observations from Mariner 4
 Images returned showed a Moon-like, cratered terrain
 Surface atmospheric pressure of 4.1 to 7.0 mb and
daytime temperatures of -100° C (-148° F) were
estimated
 No magnetic field was detected
Early Spacecraft Exploration
Mariner 4
 How did Mariner 4 advance scientific understanding of
Mars?
 Mars looked more like the Moon
 Possibility of life seemed less likely
 IMPORTANT: Mariner 4 only imaged ~1% of the surface of
Mars, mostly in the southern hemisphere
 What technological advance(s) did Mariner 4 carry?
 The Mariner 4 spacecraft
Early Exploration
How did Mariner 4 change and/or reaffirm
perceptions of Mars?
Early Exploration
Early Spacecraft Exploration
Mariner 6 & 7
 “Study the surface and atmosphere of Mars to establish
the basis for future experiments in the search for extraterrestrial life and to develop technology for future Mars
missions. The 1969 flights will not determine the presence
of life on Mars but will help establish whether or not the
Martian environment is suitable for life.”
Mariner (6 & 7) Press Kit, July 18, 1969
Early Spacecraft Exploration
Mariner 6 & 7
Early Spacecraft Exploration
Mariner 6 & 7
 Notable observations from the Mariner 6 & 7 missions
report
 Temps range between -73° C (-100° F) & 15° C (60° F)
 The polar cap was crusted with frozen carbon dioxide…
 Features with a dimension of 900 (ft.) could be identified.
 The so-called Martian canals were not in evidence.
 At a location called Nix Olympica…was a huge crater 300
miles in diameter.
 No indications of volcanism were found.
 Mariner 6 & 7 imaged 20% of the surface of Mars, mostly in
the southern hemisphere
Early Spacecraft Exploration
Mariner 6 & 7
 How did Mariner 6 & 7 advance scientific understanding of
Mars?
 Temperature range
 South polar cap composed of CO2; temp reading of -123°C
(-190°F)
 NO CANALS
 What technological advance(s) did Mariner 6 & 7 carry?
 Spacecraft with higher resolution cameras & spectrometers
Early Spacecraft Exploration
Mariner 8 & 9
 “Study the surface and atmosphere of Mars in detail, and
over a period of time, to provide a broad picture of the
history of the planet and natural processes currently
shaping the Martian environment. To accomplish this, one
spacecraft will map 70% of the planet and the other will
repeatedly study selected areas on Mars to observe
changes on the surface and in the atmosphere.”
Mariner (8 & 9) Press Kit, April 30, 1971
Early Exploration
How did Mariner 6 & 7 change and/or reaffirm
perceptions of Mars?
Early Spacecraft Exploration
Mariner 9
Early Spacecraft Exploration
Mariner 9
 Arrived at Mars only to find a global dust storm blanketing
the planet
 Circular features peaking through the dust
Early Spacecraft Exploration
Mariner 9
 Notable results from Mariner 9
 Global mapping (imaging) of the surface of Mars
 The first detailed views of the Martian volcanoes, Valles
Marineris, the polar caps, and the satellites Phobos and
Deimos
 Provided information on global dust storms, the planet’s
rugged gravity field, and evidence for surface aeolian
(wind) activity.
Early Exploration
Mariner 9
 How did Mariner 9 advance scientific understanding of
Mars?
 Mars is more geologically diverse than had ever been
presumed
 Evidence water once flowed on the surface, not in
artificial canals, but natural river channels
 What technological advance(s) did Mariner 9 carry?
 Spacecraft orbited Mars, first unmanned planetary orbiter in
history
Early Exploration
How did Mariner 9 change and/or reaffirm
perceptions of Mars?