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Tentative Topics
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Introduction
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Nature of Geography
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Human-environment tradition
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Regional geography tradition
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Spatial tradition
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Planet Earth as the human home
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Geography and Mars
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How the four traditions apply to the study of Mars
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The contribution of geography's regional tradition to exploration of a
different planet: "Areography"
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History of Mars exploration
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History of Mars observation from Earth
- The "eyeball method":
- Early astronomer/astrologers from Mesopotamia (Iraq), India, China,
Egypt, and Greece noted and described the regularities in star motions across
the sky: They also noticed that five "stars" were not well-behaved, that they
moved faster or slower than the "others," and even went backwards or
retrograde. These five wanderers ("astra planeta") were Mercury, Venus, Mars,
Jupiter, and Saturn.
- The ancient Indians mentioned a retrogation of Mars in the
Mahabharata in 3,010 BCE
- The Chaldean astronomer/astrologers of ancient Mesopotamia compiled a
database of astronomical observations that they tried to correlate with
different social, economic, and environmental events -- Mars is often
mentioned in these tablets, the Enuma Anu Enlil, which date back to 652
BCE and continued until 60 BCE. Here is a sample: "That month, the equivalent
for 1 shekel of silver was: barley [lacuna] kur; mustard, 3 kur ... At that
time, Jupiter was in Scorpio; Venus was in Leo, at the end of the month in
Virgo; Saturn was in Pisces; Mercury and Mars, which had set, were not
visible."
- Chinese dynastic historians noted conjunctions of planets including Mars
back to the fourth century BCE
- The Mayans from 1800 BCE to the time of Columbus developed elaborate and
accurate calendars, especially during their Classic phase from 250 - 900 CE.
The Spanish destroyed most of their written records, but four priestly
handbooks, or codices, survive. The Dresden Codex includes a "Mars Beast
Table" that predicts Mars' motions and retrogations.
- The ancient Greeks were really bugged by Mars' and other planets'
occasional retrograde episodes and came up with various schemes.
- Aristotle (lived ~384-322 BCE) observed an occulation of Mars by the Moon
around 356 or 357 BCE: the Moon passing in front of Mars. He figured out that
Mars had to be farther out than the Moon.
- Aristarchus (~310-230 BCE) had come up with the idea that the sun was the
center of the solar system and the planets revolved around it: He didn't get
too far with this seemingly nutty notion.
- Hipparchus (~190-120 BCE) described the five planets' orbits as
"deferents" around the earth
- Ptolemy (~90-168 CE) added little circular sub-orbits, or "epicycles"
along the deferents to account for the retrograde episodes.
- The collapse of Graeco-Roman civilization put an end to work on Mars or
any other science for a long time.
- The rise of Islam rejuvenated Arab culture and supported mathematical and
scientific work, including mastery of the Greek classics and developments on
them. Algebra and the Arabic numeral system were developed, and Ptolemy's
system was edited by Ibn al-Haytham around the 10th century and Nasir ad-Din
at-Tusi in the late 13th century to make it better able to predict planetary
motion. These achievements were brought to Europe at least partly because of
the Crusades.
- Europeans in the throes of the Renaissance and their re-introduction to
Classical era and Arab science, got into the swing of things, too:
- Mikołaj Kopernik or Nicholas Copernicus argued in 1543 that the
planets' motion made more sense if Earth was itself a planet and rotated about
a north-south axis while revolving with the other planets around the Sun. His
observations squared better with Aristarchus He assumed that all six planets'
orbits were perfect circles, which meant that there were still little
discrepancies. He was forced to account for those by keeping Ptolemy's
epicycles. This was an absolutely revolutionary idea to Christendom: That
Earth wasn't the center of creation.
- Tyge Brahe, Latinized as Tycho Brahe, was a dedicated and obsessive
observational astronomer in Denmark, Sweden, Germany, and Bohemia, who lived
from 1546 to 1601. Brahe wasn't much into theory, but he was a really
original engineer who built new observational instruments for measuring the
positions of objects in the sky. He instituted a program of nightly
observation and trained others in the art. He had kept meticulous records of
the precise locations of various stars and the planets in a huge database. He
often focussed on Mars because of its seeming anomalies of motion, but he
never theorized from his observations. He was aware of Copernicus' work, but
found it implausible because it required the abandonment of Aristotelian
physics.
- Johannes Kepler came to work with him toward the very end of his life, in
1600, and studied 20 years of his records, trying to make sense of them. He
found himself in agreement with Copernicus, which annoyed Brahe no end. So
Brahe decided not to share all his data with Kepler but set him working only
on the data concerning Mars, his toughest problem. Kepler found that the best
way to make sense of Mars' orbit was to apply Copernicus' heliocentric theory
but relax the assumption about a perfectly circular orbit. In 1609, years
after Brahe had died (some even speculate that he offed Brahe to get hold of
his data), Kepler posited an elliptical orbit for Mars and three laws of
motion and got rid of the epicycles.
- The orbits of the planets are ellipses, with the Sun at one of the two
foci of the ellipse.
- The line connecting the planet to the Sun sweeps out equal areas in equal
times, so it slows down at aphelion and speeds up at perihelion
- If you compare two planets' orbits, the ratio of the squares of their
revolutionary periods is the same as the cubes of their semimajor axes: The
period a planet requires to go around the Sun increases rapidly with the
radius of its orbit. The farther out they are, the drastically longer their
years are.
- Telescope-aided observation
- In 1609, the same year Kepler published his Laws of Motion, Galileo built
and operated the first astronomical telescope. He trained it on Mars and
began recording his observations. He was looking for evidence of Mars showing
phases like the Moon, which Copernicus and Kepler reasoned the planets would
show. His telescope was too primitive and Galileo honestly reported that he
couldn't see the changing phases but he did say Mars did not look perfectly
round to him. For his defense of Copernicus' heliocentric theory against
specific orders of the Church, Galileo got into trouble with the Inquisition
and was ordered into prison, a sentence later commuted to lifelong house
arrest.
- In 1636, another Italian astronomer, Francisco Fontana, used a telescope
to observe Mars and made the first drawing of the planet. His drawing showed
Mars in gibbous phase, showing that the planet shows lunar-like phases, as
Copernicus and Kepler expected. He also said its surface wasn't of an even
shade. His drawings show a dark spot in the middle, now thought to be a
defect in his telescope.
- In 1659, Dutch astronomer Christiaan Huygens was able to get such a good
bead on Mars that he could establish that Mars rotates around a north-south
axis and its daylength is slightly longer than Earth's. He drew maps of what
he was seeing and recorded a dark triangular patch near Mars' equator, which
we now call Syrtis Major.
- In the 1660s, Jean Dominique Cassini observed the polar caps of Mars as
bright spots. He also refined Huygens' estimate of Mars' day length to about
24 hours and 40 minutes. In 1672, he figured out the distance between Mars
and the earth by coördinating with a friend in French Guiana in South
America to take measurements at the same time. He could use this parallax to
figure out how far Mars was. From Kepler's Third Law, Cassini knew that Mars'
orbital period was roughly 1.5 times that of Earth, so, if he could figure out
how far apart Earth and Mars were at opposition, he knew that the Earth-Sun
distance would be approximately twice the Earth-Mars distance. Using this,
Cassini figured the Astronomical Unit (or Earth-Sun distance) at 140 million
km is awfully close to the actual distance known today of roughly 150 million
km.
- In 1719, Cassini's nephew, Giacomo Maraldi, noticed that his uncle's
white spots grew and shrank, and that the dark areas on Mars changed in shape.
From this, he figured Mars had seasons.
- In 1786, William Herschel also observed these changes. He was able to
surmise the angular tilt of Mars as roughly 25°, which, again, confirmed
that Mars had to have seasons. He thought the dark areas might be seas and
some of the light areas that moved around might be clouds and vapors. He also
figured that the bright polar spots were thin sheets of snow and ice. He
noticed that faint stars that passed near Mars were not dimmed, and he
inferred that meant Mars had a very thin atmosphere.
- In 1809, Honor&ecute; Flaugergues spots variations he calls "yellow
clouds" on the surface of Mars. These were probably dust storms.
- The Geographic Period: Telescopy plus mapping
- As telescopes improved, sketches of Mars did, too. In 1800, Johann
Hieronymus Schroeter makes drawings of Mars.
- People really began to look forward to Martian oppositions (when Mars is
on the opposite side of Earth from the Sun, thus lined up at their closest).
Some oppositions are closer than others, depending on where in the two
planets' orbits the opposition occurs. The 1830 one was a good one, and folks
were out there with their telescopes.
- William Beer and Johann H. von Mädler assembled the first real map
of Mars in 1840. They came up with the latitude and longitude grid used
pretty much today. They also refined Cassini's refinement of Huygens' estimate
of the Martian day: 24 hours 37 minutes 22.6 seconds.
- William Whewell started speculating about life on Mars in 1854, saying
that the dark areas might be greenish seas contrasting with red land.
- Jesuit monk Angelo Secchi draws a map in 1863 and refers to "canali" or
channels for the dark areas. He also calls the dark triangle of Syrtis Major
the "Atlantic Canal."
- In 1860, the dark areas are suggested to be vegetation, changing with the
seasons, by Emmanuel Liais.
- In 1867, Richard Anthony Proctor creates a map of Mars and his
pinpointing of the prime meridian is the one used today.
- Pierre Jules Janssen and Sir William Huggins pioneer the application of
spectroscopy to Mars in 1867. They try to detect oxygen and water vapor. They
are not successful.
- In 1873, Camille Flammarion agrees with Liais that there might be
vegetation there and wonders if it's vegetation that creates the reddish color
of Mars.
- The 1877 opposition was a doozy, which coïncides with the advent of
powerful telescopes.
- Asaph Hall was out there looking for moons, figuring Earth has one,
Jupiter has four, so Mars should have two. He was about to give up but his
wife kept after him and on the 11th and 16th of August, he spotted first one
and then the other: Phobos and Deimos.
- Giovanni Schiaparelli, head of the Brera Observatory in Milan, mapped the
dark and light features of Mars, some 65 of them, and gave them names, most of
which we still use today. His map showed a bunch of intersecting lines, which
he called "canali," just like Father Secchi did. Brownie points to anyone who
finds the big, big error in the Boyce textbook concerning Schiparelli's map.
Schiparelli's canali become a huge growth industry, the Face on Mars of his
time, taking on a life of their own in others' hands.
- William Pickering of Harvard was seeing these channels, too, but in 1892,
he saw one running across "Mare Eruthraeum," a dark area that Schiaparelli
thought might be an ocean. Realizing that a "canal" can't cut across an
"ocean," he realized something was amiss and that the dark areas were probably
not water bodies after all. Maybe vegetation he thought.
- In 1892, Edward Emerson Barnard spotted craters on Mars. No-one else
paid much attention, but it's an interesting early counterpoint to the canals
craze. He also said he tried and tried to see all these canals and couldn't
for the life of him.
- In 1893, someone gives one Percival Lowell a book about Mars for
Christmas. It bowls him over and he begins to obsess on it. Most of us
obsess on whatever craze gets our attention, but Percival Lowell was the son
of a rich Boston family with enormous resources to throw at his interests. He
decides to build an observatory in Arizona (to reduce atmospheric twinkling
due to moisture). He became a professional astronomer and in 1902 is
appointed to MIT as non-resident astronomer.
- In 1895, 1906, and 1908, he published a series of books called Mars,
Mars and Its Canals, and Mars, the Abode of Life, in which he laid
out his elaborate theories built on wild extrapolation from the data. These
linearities so many people were seeing on Mars were, in fact, canals. Such
extensive canalization he saw as signs of intelligent life, life desperate to
cope with a drying planet and engaging in planet-scale engineering to survive.
The book became a best-seller and really began to affect Western culture.
- Scientists, however, were, as usual, skeptical creatures, and a few begin
to question this canals business.
- Alfred Russell Wallace, who came up with the theory of evolution a little
later than Darwin but almost beat him to the punch in publishing it, went
after Lowell. He wrote a book describing his own experiments in measuring the
light spectra from Mars and concluded that the place was really, really cold,
about -35° F, so Lowell's claim of water canals had to be "all wet." He
figured that the polar ice caps had to be mostly frozen carbon dioxide, not
water ice. He said, near as he could tell, Mars was completely hostile to
life.
- In 1912, Svante Arrhenius argued that Mars might be covered with salts.
In winter, the water on Mars freezes and the salts take on a light, playa
color. When the warmer temperatures of summer melt the polar caps in summer,
the salts wet and darken. No life necessary.
- Other scientists reported having trouble seeing canals, let alone
anything more elaborate based on canals.
- Lowell responded to scientific criticism by turning to the public for
support, giving public lectures and writing articles for popular magazines.
In other words, he began to shun the peer review process that is the
foundation of science.
- When he did this, many other scientists began to shy away from Mars,
figuring it had become the bailiwick of crackpots.
- A few, however, got caught up in it all.
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Nikola Tesla, inventor of
Alternating Current among other things, claimed to detect radio signals from
Mars in 1899 and worked on a "Teslascope" to communicate with Mars
- Guglielmo Marconi, of radio fame, also claimed to have heard from an
alien radio transmitter a few years after Tesla's reports. Critics thought he
was just picking up another radio station's interference.
- By the time of Lowell's death, most astronomers thought that the planet
was not only uninhabited by canal-building intelligent aliens but
uninhabitable.
- Really powerful telescopes began to be aimed at Mars in the early
twentieth century: The Hale 60" telescope at Mt. Wilson in 1909 turned up
nary a single narrow, straight canal or any other geometric pattern.
- In 1913, astronomer Edward Maunder did a psychological experiment showing
how the human eye tends to see patterns linking random lines and circles and
the farther the observer was from the random pattern, the more likely they
were to report linearities linking things in the pattern.
- A few hardy souls held out for canals right up until the Mariner flybys
put the matter solidly to rest.
- New toys, new Mars: Spectral analysis
- Basic idea of spectroscopy
- Electromagnetic spectrum can be displayed along wavelengths
- Study of radiation as it is emitted, absorbed, or scattered by radiant
objects as affected by substances between it and a sensor
- Hot, dense objects emit across a continuous spectrum
- Cooler, less dense objects emit discontinuous lines
- A hot, dense radiator with a cooler, more diffuse substance between it
and the sensor will show a continuous spectrum with discrete absorption lines
- Wavelengths emitted or absorbed are diagnostic of particular elements,
compounds, or minerals
- Attempts to measure Martian air pressure through spectral analysis
- In 1862, William Higgins tried to apply the general idea to use Mars
spectra to measure its atmospheric pressure
- Mars reflected sunlight, which wasn't "illuminating"
- All that could be concluded is that Mars didn't glow
- Lowell tried to apply spectral analysis to Higgins' problem in 1908
- He estimated it as 87% of Earth's, which we know is way off
- His method of measuring gas scattering in the atmosphere could have
gotten the right answer, but he wasn't correcting for other important
scatterers, such as the very abundant dust
- Even so and despite his increasing reputation as a bit eccentric, this
approach was a pioneering contribution to the science of Mars
- Other attempts to get at Martian atmospheric pressure failed for 50 years
mainly because the composition of the Martian atmosphere wasn't known
- Ironically, the first successful estimate of the Martian atmospheric
pressure (around 5.16 mb or hPa) was done by Louise Young after spacecraft had
visited Mars and gotten the pressure directly: Her work showed that
Earth-based spectroscopy could do the job.
- Spectral analysis of Martian temperatures
- This was more successful
- Any object that absorbs energy re-radiates it as thermal energy
- Measuring thermal emissions allows inference of temperature through
Wien's Displacement Law
- Lowell Observatory measurements back to the 1920s showed Mars was one
cold place, averaging -40° C (-40° F), whereas Earth averages 15°
C (59° F). The poles were about -70° C (-94° F), while the
"warmest" place along the equator was about 10° C (or 50° F). The
highest equatorial highs were pushed higher in 1954, around 25° C (77°
F).
- Life on Mars and spectral analysis
- There is a distinct wave of darkening of the planet that extends outward
from the polar caps in spring and eventually involves much of the planet
- Many folks thought that was vegetation activity
- In 1938, Peter Millman said that the spectra from this darkening wave is
not the same as any vegetation, at least on Earth, dealing that line of
speculation a serious blow
- In 1954, W.M. Sinton said he had collected spectra in the infrared that
resembled those of various organic compounds, perhaps the result of vegetation
after all
- He later withdrew his paper, saying that he and a colleague had collected
spectra for which he had not considered the contamination of heavy water in
the earth's atmosphere that had distorted the signals he was looking at.
- Audoin Dofus and Thomas McCord said that the darkening was not green:
That was an optical illusion. The dark areas were simply less bright areas
- Imagery from near-Earth: Hubble Telescope
- Designed in 1973 after the Space Shuttle was approved as a feasible way
of getting it into space, the Hubble Telescope was funded by Congress in 1977
and launched in 1990
- It is a reflecting mirror type of telescope
- It was found to have a tiny flaw in the 2.4 m main mirror (too flat
around the edge by about 1/50th of a human hair) that gave it astigmatism.
- It was provided with corrective optics in 1993
- Its angular resolution or sharpness of focus is 0.05 arcsecond. "If you
could see as well as Hubble, you could stand in New York City and distinguish
two fireflies, 1 m (3.3 feet) apart, in San Francisco." <http://hubblesite.org>
- Focussed on Mars, its best resolution has been about 19 km
- It has monitored Martian weather, catching a springtime dust storm in
1996, keeping an eye on Mars weather patterns as Mars Global Surveyor began
aerobraking into Martian orbit in 1997, catching cloudiness there in 1997, a
polar water-based cyclone (complete with an eye) in 1999, and identifying
water-bearing minerals on Mars
- Hubble has done both visible light and infrared imaging of Mars
- Hubble took best images of Mars possible from the Earth system in August
2003, the best opposition in 59,619 years
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History of the robotic missions to Mars
- The majority of missions have actually been failures: launch failures,
orbit insertion failures, crashes
- Only about 40% have been successful
- Mars is a very dangerous target: NASA people joke about the "Great
Galactic Ghoul" that eats up spacecraft there, saying that Mars is the
"Bermuda Triangle" of the solar system, or talking bleakly about the "Mars
Curse"
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Spacecraft types
- Flyby spacecraft trajectories (Earth analogue: gravitational-assist
manœuvres by Galileo in 1990 and 1992, Cassini-Huygens in 1999, during
which calibration imagery was taken)
- Orbiters (Earth analogues: Landsat, IKONOS, SPOT, GOES, POES, DMSP)
- Probes (Galileo atmospheric entry probe at Jupiter, Cassini's Huygens
probe at Titan)
- Balloon probes (USSR Vega 1 on Venus; ESA planned multiple balloon probes
of Venus)
- Landers (well, Huygens did function for a short while after a soft
crash-landing on Titan; the Surveyor series soft-landed on the Moon to assess
the surface, take images, and do soil analyses; the USSR Venera series
included successful landers on Venus)
- Rovers (Earth analogue, sort of: portable ground-based reflectance
spectrometers)
- Penetrators (Mars 96 carried two)
- Sample return landers (taking samples and then returning them to Earth as
Genesis was to do with solar wind particles collected from the L1 point in
2004 and as Stardust did with cometary material from Comet Wild 2 in 2006)
- Missions to Mars (successful missions highlighted)
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Mars 1960A, aka Korabl 4 or Marsnik 1 (failed after liftoff 10 October 1960)
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USSR Mars 1960B, aka Korabl 5 or Marsnik 2 (failed after liftoff 14 October
1960)
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USSR Sputnik 22, aka Mars 1962A or Korable 11 (blew up on launch 24 October
1962)
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USSR Mars 1, aka Sputnik 23 (launched on 1 November 1962, flyby on 19 June
1963. but communications failed earlier so it never sent data, entered
independent orbit around sun)
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USSR Sputnik 24, aka Mars 1962B or Korabl 13 (blew up on launch 4 November
1962)
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USSR Zond 2 flyby (launched 30 November 1964, flyby on 6 August 1965, but
communications failed earlier so it never sent data)
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USSR Zond 3 orbiter (missed launch window, launched anyway on 18 July 1965,
sent to Moon where it imaged dark side of the Moon, and then went on towards
Mars as a test flight)
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NASA Mariner 3 flyby (shroud failed to open after launch, 1964)
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NASA Mariner 4 flyby (1965)
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NASA Mariner 6 flyby (1969)
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NASA Mariner 7 flyby (1969)
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USSR unnamed Mars craft (failed on launch 27 March 1967)
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USSR Mars 1969A orbiter (failed after liftoff on 27 March 1969)
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USSR Mars 1969B orbiter (failed after liftoff on 14 April 1969)
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USSR Cosmos 419 orbiter/lander (failed after liftoff on 10 May 1971)
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USSR Mars 2 orbiter/lander combination (launched May 1971, orbiter achieved
orbit in November 1971 but had telemetry problems)
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USSR Mars 2 lander crashed in November 1971
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USSR Mars 3 orbiter/lander combination (launched May 1971, orbiter
achieved orbit in December 1971;
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Mars 3 lander soft-landed in December 1971 but only transmitted part of one
image before failing
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NASA Mariner 8 orbiter (failed on launch 8 May 1971)
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NASA Mariner 9 orbiter (13 November 1971 - 27 October 1972)
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USSR Mars 4 (launched in July 1973, failure during orbit insertion February
1974, but a few images were returned)
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USSR Mars 5 orbiter (launched in July 1973, failure during orbit insertion
February 1974), but Mars 5 sent back a few images
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USSR Mars 6 lander (launched in August 1973, but crashed in March 1974)
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USSR 7 lander (launched in August 1973, but missed the planet in March 1974)
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NASA Viking 1 orbiter (1976: Orbiter 1 lasted until 1980;
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NASA Viking 1 Lander (lasted until 1982)
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NASA Viking 2 Orbiter (1976: lasted until 1978)
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NASA Viking Lander 2 (lasted until 1980)
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USSR Phobos 1 (launched on 5 July 1988, lost on 2 September 1988)
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USSR Phobos 2 (launched on 12 July 1988, lost on 29 January 1989, but a few
images were returned)
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NASA Mars Observer (launched 25 September 1992, contact lost on arrival 22
August 1993)
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Russian Space Agency Mars 96 orbiter/4 landers/2 penetrators (launched on 16
November 1996, failed to clear Earth orbit and lost soon after liftoff)
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NASA Mars Pathfinder lander/NASA Sojourner rover (1997)
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NASA Mars Climate Orbiter (launched 11 December 1998, crashed on arrival 23
September 1999)
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NASA Mars Polar Lander/Deep Space 2 (launched 3 January 1999, crashed on
arrival 3 December 1999)
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NASA Mars Global Surveyor orbiter (1997-2006)
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Japan Institute of Space and Aeronautical Science, University of Tokyo,
Nozomi, aka Planet-B or 25383 (launched 4 July 1998, unable to make planned
orbit insertion on 11 October 1999, reconfigured for a new trajectory and
orbit insertion on 14 December 2003 but last navigation correction failed and
it made a flyby instead and entered an independent orbit around the sun
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NASA Mars Odyssey orbiter (2001)
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ESA Mars Express orbiter/Beagle lander (orbiter operating December
2003-; lander lost)
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NASA Mars Exploration Rovers Spirit and Opportunity (January 2004-)
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NASA Mars Reconnaissance Orbiter (2006-)
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Remote sensing basics: Resolution
- Spatial
- Varying, as in a descending probe (e.g., Huygens' imagery of Titan's
landscapes on the way down)
- fine resolution: 0.5-5 m (e.g., IKONOS, OrbView-3)
- coarse resolution: 1 km (e.g., MODIS) - 8 km (e.g., GEOS)
- Vertical
- Vertical resolution is generally worse than horizontal
- This z coörodinate is the basis of digital elevation models (and, if
you've taken any of Dr. Wechsler's classes, you're aware of the uncertainty
issue)
- Bases for elevation extraction include laser altimeters, interferometric
synthetic aperture radar, and stereo pairing of images
- Spectral
- Electromagnetic spectrum, bands, bandwidth
- Panchromatic (all bands within a large range, often fine resolution)
- Multispectral (3-100 or so bands, at discrete intervals along the
spectrum)
- Hyperspectral (16-220 narrow bands contiguous to one another over a
spectral range)
- Temporal
- One time (e.g., flyby)
- Intermittant (e.g., AVIRIS)
- Repetitive (stationary orbits, e.g., GEOS, or regular overflights, e.g.,
Landsat)
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Sources of data on Mars available today
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NASA Mariner
4 flyby (1965)
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NASA Mariner
6 flyby (1969)
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NASA Mariner
7 flyby (1969)
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USSR Mars 3
orbiter/lander combination (launched May 1971, orbiter achieved orbit in
December 1971;
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NASA Mariner
9 orbiter (13 November 1971 - 27 October 1972)
-
USSR Mars 4
(launched in July 1973, failure during orbit insertion February 1974, but a
few images were returned)
-
USSR Mars 5
orbiter (launched in July 1973, failure during orbit insertion February 1974),
but Mars 5 sent back a few images
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NASA Viking 1 orbiter (1976: Orbiter 1 lasted until
1980;
- Visual Imaging System (VIS): twin high-resolution, slow-scan television framing cameras, with six bands in
the visible light spectrum (including one panchromatic band), yielding an image of ~40 x 44 km, of 7
bits (128 values), and 1056 x 1182 pixels.
- Infrared Thermal Mapper (IRTM): A
multichannel radiometer, with four small telescopes, each having seven IR detectors. Measured temperatures in the atmosphere and
areas on the surface. Could read temperature differences within 1° C throughout the range from -130° C to +57° C.
- Orbiter Radio Science: Two-way S-band and
X-band radio links between the earth and the orbiter generated orbiter navigation data, Martian gravitational data, interplanetary
plasmas, and information on the solar corona through Doppler shifts, time-of-flight measurements, and occulation studies. The UHF
bands used for orbiter-lander communication also generated surface and horizon information.
- Mars Atmospheric Water Detector (MAWD):
Infrared grating spectrometer, measuring reflected IR from the surface through the atmosphere. Spectral intervals were those around
water-vapor absorption lines at 1.4 microns. Provided data on the amount of water in the line of sight.
-
NASA Viking 1 Lander
(landed in western Chryse Planitia, at ~23° N and ~48° W and ~2.69 km elevation and lasted
until 1982)
- Two 360-degree cylindrical scan cameras
- Sampler arm, with a collector head, temperature sensor, and magnet
- Meteorology boom, holding temperature, wind direction, and wind velocity
- Seismometer, magnet and camera test targets, and magnifying mirror
- Biology experiment package was held in a temperature-controlled compartment on the inside of
the lander body
- Gas chromatograph mass spectrometer
- X-ray flourescence spectrometer
- A pressure sensor was under the lander body
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NASA Viking 2 orbiter (1976: lasted until 1978)
- Visual Imaging System (VIS): twin high-resolution, slow-scan television framing cameras, with six bands in
the visible light spectrum (including one panchromatic band), yielding an image of ~40 x 44 km, of 7
bits (128 values), and 1056 x 1182 pixels.
- Infrared Thermal Mapper (IRTM): A
multichannel radiometer, with four small telescopes, each having seven IR detectors. Measured temperatures in the atmosphere and
areas on the surface. Could read temperature differences within 1° C throughout the range from -130° C to +57° C.
- Orbiter Radio Science: Two-way S-band and
X-band radio links between the earth and the orbiter generated orbiter navigation data, Martian gravitational data, interplanetary
plasmas, and information on the solar corona through Doppler shifts, time-of-flight measurements, and occulation studies. The UHF
bands used for orbiter-lander communication also generated surface and horizon information.
- Mars Atmospheric Water Detector (MAWD):
Infrared grating spectrometer, measuring reflected IR from the surface through the atmosphere. Spectral intervals were those around
water-vapor absorption lines at 1.4 microns. Provided data on the amount of water in the line of sight.
-
NASA Viking Lander 2
(landed in Utopia Planitia, ~200 km west of Crater Mie, ~48°N and ~226&Deg;W, 4.23 km in
elevation and lasted until 1980)
- Two 360-degree cylindrical scan cameras
- Sampler arm, with a collector head, temperature sensor, and magnet
- Meteorology boom, holding temperature, wind direction, and wind velocity
- Seismometer, magnet and camera test targets, and magnifying mirror
- Biology experiment package was held in a temperature-controlled compartment on the inside of
the lander body
- Gas chromatograph mass spectrometer
- X-ray flourescence spectrometer
- A pressure sensor was under the lander body
-
USSR Phobos 2 (launched on 12 July 1988, lost on 29 January 1989, but
a few images were returned)
-
NASA Mars Pathfinder
lander/NASA Sojourner rover (1997)
- Atmospheric Structure Instrument/Meterology Package (ASI/MET): A set
of temperature (one thin wire thermocouple for measuring temperature during
descent and three for continuous post-landing measurement at 25, 50, and 100
cm above the surface), pressure (Tavis magnetic reluctance diaphragm sensor),
and wind sensors (six hot wire elements around the top of the lander mast and
three aluminum cone wind socks)
- Alpha Proton X-Ray Spectrometer (APXS: Derived
from Russian Vega and Phobos missions and identical to the APXS on the doomed
Mars 96 mission. APXS is mounted on the Sojourner Rover body, with its sensor
head on a deployment mechanism carried by the rover. The emission of alpha
particles at a target creates a scatter of alpha particles from the atomic
nuclei of chemicals on and in that target. Similarly, protons are also sent
off by alpha particle interactions with the nuclei of certain elements with
atomic numbers from 9-14 can be collected and characterized. Also, alpha
particles excite atoms and they then emit X-rays, which can be characterized
by signature emission patterns associated with each element.
- Imager For Mars Pathfinder IMP: A stereo
imaging system with selectable filters allowing multipspectral color
detection.
-
NASA Mars Global Surveyor
orbiter (1997-2006)
- Mars Orbiter Camera (MOC) creates daily wide-
angle weather-focussed images of Mars, as well as narrow angle images. It can
pick out surface features as small as 1.4 m.
- Mars Orbiter Laser Altimeter (MOLA): Transmits
infrared laser impulses toward the Martian surface at 10 Hz and receives the
reflected light. It measures the time-of-flight and infers the distance
between the MGS and the surface. With millions of these impulses recorded and
processed, MOLA has generated a digital elevation model of Martian topography.
This is often shown in hypsometric tinting, cartographically strongly
suggestive of a previous oceanic era on Mars. "Persuasive cartography"?
- Thermal Emission Spectrometer (TES):
Measures the thermal infrared radiation emitted by the Martian surface,
revealing geological and atmospheric information. Has collected over
200,000,000 infrared spectra so far, and served as the basis for maps of
atmospheric dust loading and temperature distributions.
- Electron Reflectometer (MAGNETOMETER):
Measures magnetism on Mars. The Martian magnetic field collapsed long ago but
there are remnant signs of magnetism on the surface. The MAGNETOMETER has
mapped these local sources and allowed modelling of the Martian interaction
with the solar wind
- Gravity Field Experiment (RADIO
SCIENCE): Maps anomalies in the planet's gravitational field by measuring
minute tugging effects registered by the spacecraft's high-gain antenna, its
telecommunication system, and the onboard ultra-stable oscillator.
-
NASA Mars Odyssey
orbiter (2001)
- THEMIS
Thermal Emission Imaging System: Two independent multispectral scanning
systems, with five visible light bands (with 19 m pixels) and ten infrared
bands (with 100 m pixels). THEMIS focusses on identifying water and ice.
- GRS
Gamma Ray Spectrometer: The sensor package is mounted at the end of a 6 m
boom. It detects gamma rays emitted by the Martian surface due to its
exposure to the highly energetic cosmic ray radiation from stars (including
the sun). These emissions, collected by the Gamma Sensor on GRS form
signature energy distributions that identify the chemistry of the emitting
surface. Neutrons are also produced by this exposure (indeed, it is their
release that excites surface chemicals into emitting gamma rays), and these
are collected by the HEND and Neutron Spectrometers on the GRS. GRS has been
used to create maps of hydrogen abundance in the upper meter of the Martian
surface, and hydrogen abundance indicates water (H2O).
- MARIE
Martian Radiation Environment Experiment: An energetic particle spectrometer
that focusses on the radiation environment during the cruise to Mars and in
the near-Mars space environment. This instrument is intended to characterize
the space radiation hazard for astronauts en route to or on the surface of
Mars.
-
NASA Mars Exploration Rovers (MER) Spirit and
Opportunity (January 2004-)
- Rovers
- Spirit in Gusev Crater
- Opportunity in Meridiani
- Instruments
- Panoramic Camera (Pancam:
A stereoscopic pair of CCD cameras with 4,000 x 24,000 pixel resolution and a
filter wheel that allows for 8 different wavelength bands per camera (11 in
total for the pair) to be imaged separately, giving Pancam multispectral
imaging capacity. The stereoscopic pairing affords parallax and depth
perception. Pancam is used to scan the horizon to identify landforms of
possible relevance to the search for evidence of water, to map the rovers'
whereabouts, and to pick interesting soils and rocks for further
investigation. It is also part of the navigation system, using filters to point at the sun to get an absolute bearing. The Pancam
team has put a lot of its imagery online.
- Microscopic Imager (MI): Mounted on
the robotic arm of the rovers, the MI ombines a microscope with a CCD camera of 1024 x 1024 pixel resolution and broad-band spectral
resolution in black and white.
- Engineering Navigation Cameras (Navcam): A stereo pair of black and white
visible light cameras that generate a 3D panoramic view of the areas around
the rovers.
- Four Engineering Hazard Avoidance Cameras (Hazcam): Mounted front and
back along the lower portion of the rovers, the Hazcams are b/w visible light
cameras mounted rigidly on the rovers to help spot obstacles or changes in
elevation that could disrupt the rovers.
- Miniature Thermal Emission Spectrometer (Mini-TES):
An infrared spectrometer that helps identify minerals (such as the
water-diagnostic carbonates) by their thermal emissivity spectral signatures.
Through a clever mirroring system, the Mini-TES can view the same objects and
features at the same time as the Pancam.
- Mössbauer Spectrometer (MB):
Dedicated to the spectroscopy of iron-bearing minerals. Its sensor head is
mounted at the end of the robot arm, while its electronics are housed in the
Warm Electronics Box on the body of the rover.
- Alpha Particle X-Ray Spectrometer (APXS):
This instrument has a small supply of radioactive alpha-particle emitters. An
alpha-particle stream is directed at a target, which excites the molecules in
the target. The alpha particles are reflected back into the instrument, along
with X-rays that may have been emitted due to the excitation. The energy
distribution signature of the returning alpha particles and the emitted X-rays
allow characterization of the chemicals in the target object.
- Rock Abrasion Tool (RAT):
Allows Martian rocks to be manipulated for further analysis. Over a two hour
timeframe, it grinds holes about 45 mm in diameter and about 2 mm deep,
exposing unaltered subsurface minerals for analysis. If these are different
from the surface materials, the difference allows inference of the processes
operating to alter the surface. The RAT was developed by Honeybee Robotics,
which maintains a web
site for the RAT's work.
- Magnet
Arrays: Three sets of magnets are housed on the RAT, the front of the
rover (but reachable by the APXS and MB instruments), and the top of the rover
deck within sight of the Pancam. They collect magnetized dust generated by
the RAT, magnetized dust that just settles on the rovers, and even magnetized
dust in motion carried by winds passing over the rovers.
-
NASA Mars Reconnaissance Orbiter (MRO) (2006-)
- HiRISE (High
Resolution Imaging Science Experiment): telescopic visible light camera with
~1 m resolution and near-infrared at ~30-60 cm pixels allowing resolution of
objects ~1.2 - 2.4 m
- CTX (Context
Imager): coarser resolution camera of a larger area to provide a regional
context for HiRISE close-ups (~30 km swaths at 6 m per pixel)
- MARCI (Mars Color
Imager): 5 visible light bands and 2 ultraviolet bands to observe Martian
climate and generate daily weather reports of dust storms and changes in
ozone, dust, carbon dioxide, and the polar caps
- CRISM (Compact Reconnaissance
Imaging Spectrometers for Mars): visible and infrared spectrometers creating
maps resolved at ~18 m, meant to identify spectral signatures associated with
minerals that precipitate out of water
- SHARAD (Shallow Subsurface Radar):
15-25 MHz frequency radar designed to penetrate the Martian surface down to a
depth as great as 1 km. It looks for changes in the electrical reflection
characteristics of the radar return that might indicate water or ice. The
horizontal resolution of this instrument is about 0.3 - 3 km and the vertical
resolution is about 15 m in free space and 10 m underground.
- MCS (Mars Climate Sounder): observes temperature, humidity, and dust by
measuring changes in atmospheric temperature or composition with height in 9
different channels, 1 spanning the visible light and nearby wavelengths (0.3-3
microns) and 8 in the thermal infrared (12-50 microns). MCS looks at the
Martian horizon from orbit, creating a vertical layering of readings
-
ESA Mars
Express orbiter (orbiter operating December 2003-)
- ASPERA-3 Analyser of Space Plasmas and
Energetic Atoms: Focusses on the solar wind's interactions with the Martian atmosphere. The goal is to see how water vapor and
other gasses escaped the Martian system.
- HRSC High/Super Resolution
Stereo Colour Imager: A stereoscopic multispectral camera that can reach a 2 m resolution of surface features. The goal is a
geological map showing the location of different minerals and rock types.
- MaRS Radio Science Experiment:
Uses the radio communication signals between the earth and the orbiter to do
some "free" imaging of Mars' ionosphere, atmosphere, surface, and interior
(through gravity effects).
- MARSIS Subsurface Sounding
Radar/Altimeter: A ground-penetrating radar instrument (1.3-5.5 MHz) that can reach as far as 5 km below the surface of Mars to
look for radio echoes from subterranean water layers and also analyze the ionosphere of Mars.
- OMEGA IR Mineralogical Mapping
Spectrometer: Has two channels, 0.5-1.0 microns (visible light) and 1.0-5.2 (infrared), each of which is imaged by a telescope, a
spectrometer, and an optical device. A major goal is identifying carbonates, which should be present if water is or was present on
Mars.
- PFS Planetary Fourier
Spectrometer: Like OMEGA, PFS will collect spectra, but over a wider band of infrared wavelengths (1.2-45 microns) in order to
focus on minerals in dust in the Martian atmosphere. It will also infer temperature and pressure measurements for carbon dioxide by
concentrating on the 15 micron carbon dioxide absorption band.
- SPICAM UV and IR Atmospheric
Spectrometer: Contains two sensors, one for UV light (118-320 nanometers), and the other for IR light (1-1.7 microns). The UV
sensor will be used to collect stellar occultation readings of the atmosphere by being pointed at the horizon, limb readings by
pointing at the horizon without a star in sight to get at Mars' atmospheric UV glow, and at the nadir to measure atmospheric
absorbtion of UV and IR directly between the orbiter and the surface below. The IR sensor will be used only in nadir mode.
-
ESA Rosetta Mission to Comet 67
P/Churyumov-Gerasimenko
- Late-breaking news: Rosetta does successful gravitational-assist
swing-by Mars
- Carries OSIRIS package of Wide Angle Camera and Narrow Angle
Camera (Optical, Spectroscopic, and Infrared Remote Imaging System)
- Images in the ultraviolet through visible light to near-infrared (0.25 to 1.00 microns)
-
Mars in space
-
Orbital characteristics
-
Orbital Eccentricity
- Orbits are slightly elliptical
- The major focus of Mars' or Earth's orbit is inside the Sun
- The plane of that orbit is called the plane of ecliptic or just the
ecliptic
- Mars' plane of ecliptic nearly parallels that of the earth (and most of
the planets except Pluto, whooops, not a planet, so its 17° orbital
inclination doesn't really count any more <G>)
- This alignment of orbits along a common group ecliptic makes sense, since
they all formed as gravitational accretions in the same solar disk of gasses
and dust
- This disk formed when the primordial proto-solar nebula, by rotating,
generated centrifugal force that gradually flattened it
- The diameter of the planet's orbit along its long axis is the major axis; half that distance (from the center of the orbit to
the orbit itself where it crosses the major axis) is called the semi-major axis ("half axis")
- The diameter of the planet's orbit along its short axis, 90° along
the plane of ecliptic from the major axis, is called the minor axis
- Half that is, of course, the semi-minor axis
- If we measured the distance between the very center of the planet's orbit
to the focus, or Sun, and then divided that distance by the semi-major axis,
we would have the eccentricity of the planet's orbit
- For Mars, that eccentricity is 0.0934, one of the largest in the solar
system at this time: Only Mercury and Pluto are more eccentric (for Earth,
it's only 0.0167)
- Animation of Earth's and Mar's revolutions through their orbits and how
that would affect how you would see Mars in a telescope http://www.windows.ucar.edu/tour/link=/mars/mars_orbit.html
-
Distance from the sun (semi-major axis): 227,936,640 km (compared with
Earth's 149,597,890 km)
- Perihelion distance: 206,600,000 km (Earth: 147,100,000 km). Perihelion
distance is the distance between the planet and the focus at the point the
planet crosses its orbit's semi-major axis at the closest approach to the Sun
- Aphelion distance: 249,200,000 km (Earth: 152,100,000 km). Aphelion distance is the distance between the planet and the focus
at the point the planet crosses its orbit's semi-major axis at the farthest approach to the Sun
- Martian perihelion is only 82.9% of aphelion (for Earth, perihelion is
96.7% of aphelion)
- Where the difference in energy receipt on Earth between perihelion and
aphelion is trivial (at least as long as perihelion takes place during the
more oceanic hemisphere's summer, around 3 January), it is a significant
seasonal driver on Mars
-
Changes in eccentricity
- Planet's orbits change in shape through time, oscillating from nearly
circular to more eccentric
- Earth's varies from ~0.01 to ~0.05 over a period of roughly 100,000 years
- Mars' varies from ~0.00 to ~0.14
-
Rotational characteristics
-
Axial tilt:
-
Mars' is 25° 11' 24" (25.19°) from the vertical of the plane of ecliptic
-
Earth's is 23° 26' 24" or 23.44° from the vertical of the plane of ecliptic
-
Precessional change in axial tilt
-
Mars takes 93,000 Martian years or ~125,000 Earth years to precess 360°
-
Earth takes ~25,765 years to precess a full 360° or about 1 ° per 71.6 years
-
Size:
-
Equatorial radius: 3,397 km (Earth: 6,378 km)
-
Equatorial circumference: 21,344 km (Earth: 40,075 km)
-
Volume: 163,140,000,000 km3 (Earth:
1,083,200,000,000 km3
-
Mass: 641.85 x 1018 metric tons (Earth: 5,973.70 x 1018
metric tons)
-
Equatorial surface gravity: 3.693 m/s2 (Earth: 9.766
m/s2)
-
Shape
-
Composition
-
The moons of Mars: Phobos and Deimos
-
Possible origins
-
Phobos: distance from Mars, direction of revolution, ellipticity, and orbital
decay
-
Deimos: distance from Mars, direction of revolution, ellipcity, and possible
orbital recession
-
Effects on Mars' axis
-
Martian palæomagnetism and the solar wind
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