Why explore other planets
To understand:
- How our solar system was formed
- Variety of planets and complexity of planetary motion
Mars
Has similar characteristics to Earth
- Has seasonal activity
- Visible changes to the surface because of seasonal activity
The most likely location for life beyond earth
After the moon, the next location in our solar system that will see humans on its surface
Mars: Pre-spacecraft era
This has been observed for a long time
Has a distance orange-red dusty hue
- Led to its name Mars (Ares), God of War
Has a retrograde behavior
- westwards motion rather than eastwards
The ice caps were seen to shrink and grow suggesting seasonal activity
The dark surface was also seen to change/occur rhythmically
- possibility of vegetation
Mars: Facts, before the space age
Diameter: 6,792 km
Density: 3.93 gm/cm^3
Year: 687 Days
Day: 24h 37m
Average distance from the sun: 1.53 AU
Number of satellites: 2 (Phobos and Deimos)
Mars: Spacecraft exploration
Mariners 4, 6, and 7 were flyby missions
Mariner 9:
- An orbital mission
- Volcanoes and Rift valleys and signs of past water (dried-up rivers and lakes)
The largest volcano is on Mars
Volcanism on Mars
Olympus Mons
- The largest volcano in the solar system
- 30km higher than the mean Mars surface
- It was active relatively recently 100 million years ago
Viking life science experiment
One of the main missions was to search for signs of life
- Looked for signs of respiration, absorption of nutrients, and gas exchanges
Results were largely inclusive for life but suggested chemical reactivity instead
Two Martin Moons
Phobos and Deimos
Mars has two small, football-shaped satellites that move in orbit close to the surface of the planet
They may be captured asteroids, or formed in orbit around Mars
Partial Eclipse
- Either Phobos or Deimos pass in front of the sun, some of the bright surface is obscured but not all
Liquid water on Mars
Runoff channels
- Estimated at ~4 billion years old
Outflow Channels
- Much larger than runoff channels, suggesting “flood water” volume
Gullies
- Young features are found on steep mountains and cloff faces
- Hydrated salts detected in the gullies
Surface Topography
Areas are comparable to continental land areas on Earth
2 hemispheres are quite different
- Range elevation of 31km
Northern hemisphere
- Smoother
- Younger
- Lower elevation
Southern hemisphere
- More rugged
- Mountainous
- Older
Dust stories can envelop the planet for weeks
MEER mission
Expected to last at least 90 sols (Martian Days)
- lasted 7 - 14 years
Establish geological evidence for past presence of water
- Both rovers found copious evidence of standing and flowing water in the past
Ice caps
Permanent
- smaller water ice cap
Seasonal
- larger
- Dry ice carbon dioxide cap
The northern ice cap is larger, colder of the 2 caps, and many km thick
When CO2 cap sublime the atmospheric pressure rises considerably
More fact about Mars
Atmosphere is about 1% as thick as Earth
Carbon dioxide (95%)
Nitrogen (3%)
Argon (2%)
No global magnetic field
- Indication of one in the past
Soil
- Mostly clays and iron oxides
- Giving Mars its characteristic color
Why did Mars change
Once a lot like Earth
- About 4 billion years ago
small planet
- cools quickly solidifying their cores, and removing magnetosphere
so the atmosphere can be stripped away by the solar wind
Low gravity also contributes to atmospheric loss
- water mist evaporates
7 minutes of terror
Having to go from Mars orbiting speed to a speed of 0 in 6 - 7 minutes without direct communication
Mars helicopter
Scout terrain where rovers cant go
Sample return
Perseverance is to create rock samples in sample tubes that can be returned to Earth for analysis
NASA and ESA plan the sample return mission by the end of the decade
Mars rock already exists on Earth in the form of meteorites
ALH 84001
Fromed at around a temperature of 18C based upon oxygen- 18 and carbon - 13 isotope measurements in carbonate nodules
Left Mars 17 million years ago and made it to earth 13 00 years ago
suggests the existence of nanobacteria
- 20 - 100 nanometers in length
- Much smaller than the equivalent bacterial structures on Earth
Had magnetic crystals
Contains polycyclic aromatic hydrocarbons
Searching for life
Prebiotic chemistry
- process from nonliving to living
Sample evidence for life turning “underground’ away from the harsh surface conditions
Methane on Mars
Methane on Mars
A surprising amount of variation was detected in methane levels on Mars
Methane can’t survive in the Mars atmosphere meaning some source of replenishment is occurring
Geologic and or biological processes could be contributing so no definitive detection of life can be claimed at this time based on methane detection
Going to Mars
~ 8 months to mars
- ~1+ year on Mars is required before returning
- ~8 months back
- such mission would be ~34 months in length
In 2010 cost of 500 billion was estimated for such a mission
A One - way mission has been suggested
The existing record for the longes consecutive space flight is 438 days by cosmonaut Valeri Polyakov, and the most accrued time in space is 878 days by Gennady Padalka
- Enough for the Mars mission and back
Human on the surface of Mars
Need to be able to grow adequate food
An environment that restricts radiation exposure will be required
Technological challenges exist
Communication with Earth will be possible for most of the time
- Except when the planet is in conjunction with the sun
- The direct line of sight to Earth will be interpreted by the sun
Instantaneous communication is not possible
Where on Mars should we settle
In lava tubes or cave system
low elevation like Hellas Plantia
- Where atmospheric pressure is relatively high for Mars
where ice can be excavated easily and solar energy is available all year long
