Mars Attacks! - Hubble Space Telescope

Transcription

Mars Attacks!
The Myth and Science of the
Red Planet at Opposition
Jim Manning
Head, Office of Public Outreach
“No one would have believed in the last years of the
nineteenth century that this world was being
watched keenly and closely by intelligences greater
than man’s and yet as mortal as his own; that as
men busied themselves about their various
concerns they were scrutinized and studied,
perhaps almost as narrowly as a man with a
microscope might scrutinize the transient creatures
that swarm and multiply in a drop of water . . .
. . . Yet across the gulf of space, minds that are to our minds as ours are
to those of the beasts that perish, intellects vast and cool and
unsympathetic, regarded this earth with envious eyes, and slowly and
surely drew their plans against us . . .”
H. G. Wells, 1898
The War of the
Worlds!
The War of the
Worlds!
Opposition!
Nergal
Ares
Mars
Opposition: Mars lies opposite the sun in the sky.
It rises at sunset and sets at sunrise.
Mars appears its brightest in the sky.
Inner Solar System
(Sun/planet sizes not to scale.)

Planets closer to the sun
move faster in their orbits
under the influence of the
sun’s gravity.

Closer (faster) planets will
periodically pass farther
(slower) planets in their
respective orbits.

Conclusion: Faster Earth
periodically “laps” and
passes slower Mars
(every 2 years, 2 months).
Opposition of Mars

When Earth laps and
passes Mars, Mars lies
opposite the sun in space
as seen from Earth.

Earth and Mars are at their
closest.

Mars appears brightest in
the sky and biggest in our
telescopes.
Not All Oppositions Are Equal

Earth’s orbit is slightly elliptical
(oval), Mars’ is moreso.
Depending on where in they
are in their respective orbits,
their separation is larger or
smaller.
The separation is least when
Mars is near perihelion--its
closest to the sun.
Mars is closest and biggestlooking at “perihelic
oppositions” (like 2003) . . .
. . .or thereabouts (like 2001
and 2005).
Not All Oppositions Are Equal

Mars will appear 20” wide (1/180 degree, 1/90
the diameter of the moon) at the 2005
opposition--similar to 2003, with one big
difference.
Mars will be higher in the sky (Yay!).
We look at it through less air and can see it
better.
Mars is Still a Small Target
If the Earth were a foot wide . . .
•The moon would be a three-inch
wide ball 30 feet away.
•Mars would be a six-inch wide
ball just over a mile away at this
opposition.
Why do Earth and Mars “attack”
each other at opposition?
Because they’re closest then-observing is best and it’s
easiest to travel from one to
the other.
And perihelic oppositions are the
best of all!
“Once in about every fifteen years a startling visitant
makes his appearance upon our midnight skies--a great
red star that rises at sunset through the haze about the
eastern horizon, and then, mounting higher with the
deepening night, blazes forth against the dark
background of space with a splendor that outshines
Sirius and rivals the giant Jupiter himself . . .
. . . That star is the planet Mars, large because for the moment near, having
in due course again been overtaken by the Earth, in her swifter circling about
the Sun, at that point in space where his orbit and hers make their closest
approach . . .
. . . Of all the orbs about us . . . he holds out the most promise of response
to that question of which man instinctively makes as he gazes up at the
stars: What goes on upon those distant globes? Are they worlds or mere
masses of matter? Are physical forces alone at work there, or has
evolution begotten something more complex, something not unakin to what
we know on Earth as life? It is in this that lies the peculiar interest in Mars.”
Percival Lowell, 1895
Observing at Opposition
1666
Giovanni Cassini

1659
Christiaan Huygens
Early telescope observers began to see and sketch dark markings and polar
caps on Mars.
Through the 1800’s, observers mapped features, calculated the Martian day
(24.65 hours), noted clouds, and watched its polar caps grow and shrink with its
seasons.
The 1877 Opposition

Asaph Hall discovered two tiny
moons in August.

Phobos (Fear)
Deimos (Panic)

The 1877 Opposition

Observed Mars at its perihelic opposition.
Created a Martian areographic
nomenclature still used today.
Mapped “canali” (channels).
Giovanni Schiaparelli
The Lowell Factor

Turned “canali” into canal.
Sketched many canals during 1894
opposition.
Published Mars in 1895.
Percival Lowell
Lowell’s Reasoning

When the polar caps melted in their
respective springs and summers,
water “greened” the landscape, and
the dark markings grew.

But thirsty Martians funneled the
runoff into into great canals that
transported the water to the
equatorial regions and the oases
supported there.

These canal and oases featured
showed up as the polar caps shrank
and water was directed toward the
equator.
Spring
Summer
“To review, now, the chain of reasoning by which we
have been led to regard it probably that upon the
surface of Mars we see the effects of local intelligence.
We find, in the first place, that the broad physical characteristics of the
planet are not antagonistic to some form of life; secondly, that there is an
apparent dearth of water upon the planet’s surface, and therefore, if beings
of sufficient intelligence inhabited it, they would have to resort to irrigation
to support life; thirdly, that there turns out to be a network of markings
covering the disk precisely counterparting what a system of irrigation would
look like; and, lastly, that there is s set of spots placed where we should
expect to find the lands thus artificially fertilized, and behaving as such
constructed oases should.
All this, of course, may be a set of coincidences, signifying nothing; but the
probability points the other way.”
Percival Lowell, Mars, 19895
The Lowell Factor

Established Lowell Observatory,
1896 in Flagstaff, Arizona.
Continued observations with 24”
Alvan Clark refractor.
Published more books.
Catch: few other observers ever
saw canals!
Observations Lead to War!

Lowell inspired Wells’ 1898 War of the
Worlds.
First novel of interplanetary war.
World saved by bacteria.
H. G. Wells
Lowell’s canals ultimately proved to be optical
illusions . . .
But the notion of life on Mars--the most
Earthlike of the other planets--fueled an
ongoing fascination with the Red Planet.
Mars in Popular Culture
War of the Worlds--The Movie
The Great Halloween Scare

October 30, 1938.

Orson Welles & the “Mercury
Theater of the Air” staged a
radio version of War of the
Worlds.

Panicked people in a warjittery nation who thought it
was for real.
Sizing up the Foe

Tantalizing . . .
Most Earth-like of the planets.
Similar “day,” longer year.
Similar tilt.
Seasons (twice as long).
Familiar features (polar caps,
weather, thin atmosphere,
markings).
Small.
Cold.
Lower gravity.
Red (rusty soil).
Reachable.
The Counterattack Begins

Mariner 4 flyby - 1965.
First close-range images.
“It’s dead, Jim.”
The Counterattack Begins

Mariner 6, 7 flybys - 1969.

Mariner 9 orbiter - 1971.
Arrived during global dust storm.
When the storm cleared, the real
Mars was revealed!

Mariner 9
Olympus Mons peeping through.
“Look, Ma, ‘canali’ after all!”
The Vikings Land (& Orbit)

Viking 1 & 2 (landers/orbiters).
Established beachhead - 1976.
First Mars landings.
Long-term study of Mars.
Volcanoes . . .
And canyons . . .
And channels, oh my!
(And splash craters.)
Life Signs?

Viking scratched the
surface looking for evidence
of primitive life.

Found nothing definitive.
But what about that “face”?
Pathfinder

Airbag bombardment 1997.
Rock-hunter.
More Earth-like than
expected.
Precursor to MERs.
Mars Global Surveyor

Arrived 1997.
Long-term reconnaisance of
surface, weather patterns.
Includes mosaic mapping of
complete surface.
Mars Global Surveyor Gallery
Surveyor Gallery Mars Global
About That Face . . .
Viking view

MGS view
Mars Global Surveyor showed the
face to be a weathered butte.
Oops.
Keep looking . . .
Mars Odyssey

Arrived in 2001.
Looking for evidence of water
ice beneath surface.
Found it! (Blue areas.)
Enough to fill several lakes
within a few feet of the surface.
Mars Express

European Space Agency.
Arrived 2003.
Stunning imagery, detected
methane.
Mars Rovers

Launched in June, 2003.
Bounced to a landing in
January, 2004.
Spirit in Gusev Crater
Opportunity on Meridiani
Planum.
Mars Rovers
Mars Rovers

Found evidence of past liquid
water.
Sedimentary rock layers.
Concretions.
Concentrations of evaporates
(salts).
Evidence for past conditions
suitable to support simple life if
it lasted long enough.
Consolidating Territory
Have We Already found Evidence for
Past Martian Life?

Some scientists claim it
contains evidence of past
Martian microbial life.

We know it’s from Mars
because its composition
and trapped gases have
the same makeup as the
thin Martian atmosphere.
Mars Meteorite History

Igneous rock solidified on Mars
4.5 billion years ago.
Ejected into space 16 million
years ago by an large meteorite
impact.
Wandered in orbit around the sun
until . . .
It ran into Earth and hit Antarctica
13,000 years ago.
Picked up by scientists in 1984.
Recognized as Martian in 1993.
Controversial evidence of past life
announced in 1996.
The Evidence . . .
•Complex organic molecules (polycyclic
aromatic hydrocarbons) in cracks.
•Carbonate globules embedded in matrix.
•Magnetite chains.
•Microscopic shapes resembling
“nanobacterial” fossils
Did Mars Start Out Like
Yellowstone?

Yellowstone National Park
has geothermal features--hot
water systems powered by
volcanic activity.
Yellowstone?

Thermophiles--heating-loving
cyanobacteria, flourish in
conditions near the boiling
point of water, in large
bacterial mats.
Yellowstone?
•Mars had volcanoes--a source
of heat . . .
•And shows evidence of past
liquid water . . .
Yellowstone?
Mars Reconaissance Orbiter

Launched August 12, 2005.
Arrives march, 2006 (for aerobraking into its work orbit).
Begins observations in November, 2006.
Why oppositions are a
good time to go . . .
HST Views Opposition

In 2003, Hubble shot Mars just
before a global dust storm
began that obscured the
surface for some months.
HST Views Opposition

In August, 2005, Hubble shot
Mars at its closest approach in
60,000 years.
Our view has changed over the years . . .
Lowell’s view
Or has it, really? The
old fascination with
Mars remains.
Hubble’s view
Will We Find the Martians?
We already have . . .
Will We Go Looking?
If we do, we’ll find the Martians . . .
And they will be us . . .
Mars Observing at the Maryland
Science Center

Fri, 9/28 5:30 - 9:30
Sat. 9/29 6:30 - 9:30
Sun, 9/30 6:30 -9:30
Fri, 11/4 5:30 -9:30
Sat, 11/5 6:30 - 9:30
Sun, 11/6 6:30 - 9:30
Mon, 11/7 6:30 -9:30
Admission is free
Call 410-545-2999