MSL carries the biggest and the most robust Mars rover ever built. Her name is Curiosity. It is 3.0 m long and 900 kg I n weight, where 80 kg are accounted for the weight of scientific instruments (the biggest rover scientific payload ever). Unlike previous rovers which work(ed) on solar energy, Curiosity carries a radioisotope power system that generates electricity from the heat of plutonium’s radioactive decay. This will provide the rover with solar independent power for at least for a full Martian year (687 Earth days) or even longer.
MSL is planned to land into the Gale Crater, which is 154 km in diameter and is thought to be at least 3.5 billion years old. It also has a 5.5 km high mountain (or mound) of debris around its central peak. This mound is composed of some layered material which might be eroded remnants of sedimentary layers originated from the bottom of ancient Martian lake.
The science objectives for this mission are:
- To determine whether or not Mars has or had the potential for life and to determine whether or not it has been (or may be still is) a habitable place for a microbial life or some other forms of life.
- To do a climate research and to determine a composition of Martian atmosphere.
- To study the rock and soil record on Mars in order to understand its geologic processes.
- To demonstrate an ability to land large, heavy payloads on the surface of Mars, which will pave the road for future human exploration.
For me, the most interesting part of MSL design is its landing vehicle, but I am going to write about it in my next post. In this post, I am trying to provide an overview of the 40 years evolution of Mars rovers – from Mars 2 (1971) to Curiosity (2012).
1971 – 14 years after the beginning of space exploration era
They both contain of an orbiter and a lander. And both landers carried Prop-M rovers on board to study the Martian surface. Unfortunately, the Mars 2 lander crashed into the Martian surface at landing, while the Mars 3 failed right after landing. Mars 3 rover, however, manage to send images from the Martian surface for first 20-seconds after landing.
The mission objectives for both Mars 2 and Mars 3 (including both orbiters and rovers) were to image the Martian surface and clouds and measure its properties, determine the temperature on Mars, provide images of Martian topography, study the solar wind and the Martian magnetic fields, and to gather information for future explorations.
I should mention here that for both Mars 2 and Mars 3 missions its orbiters were quite successful. They finished their mission by 22 August 1972, after completing 362 orbits for Mars 2 and 20 orbits for Mars 3 and sent back 60 images.
But, let’s return to the Mars Prop-M rovers.
They were small creatures of 4.5 kg weight that suppose to move across the Martian surface on skis. They were built to be connected to the lander with a 15-meter umbrical cable for power supply and communication. In order to avoid possible obstacles, two small metal rods were attached to each rover.
As science payload, each rover carried a telecam, a dynamic penetrometer and a radiation densitometer to test the strength of soil. They were supposed to stop after every 1.5 m to take images and soil measurements.
These rovers were the first human artifacts to impact the surface of Mars. Just imagine this cat size creature, almost as blind as newborn kitten trying to explore the Mars surface. What did people know about Mars 40 years ago? Almost nothing. Of course, it was the time of Cold War and competition between USA and USSR in space exploration was high.
I can’t help believing that ancient Polynesians on their catamarans were more confident and knew more about Pacific Ocean than we knew about Mars that time. So sending these rovers to Mars with the current knowledge about the planet was a really ambitious project.
1997 – 40 years after the beginning of the space exploration era
The next Mars rover was sent to Mars only 26 years after. It were though times in Mars exploration. Mars Pathfinder carried a lander and a robotic rover Sojourner. They were launched on December 4, 1996 by NASA and landed on Mars on July 4, 1997 on Ares Vallis.
Sojourner was a 10.6 kg wheeled robotic rover, not very big (65x48x30cm – a size of a dog) that carried an imaging system, alpha-proton X-ray spectrometers, a laser hazard detection system and wheel abrasion and material adherence experiments.
Sojourner generates most its power using a small solar array and it also used batteries, just in case of Mars sand storm that will block sunshine and prevent use of solar energy. During its operation time (83 sols), it sent 550 photographs to Earth and analyzed the properties of 16 locations near the lander.
Mission objectives were
- To prove that the development of “faster, better and cheaper” spacecraft was possible
- To demonstrate NASA’s commitment to low-cost planetary exploration (under 280 million $$).
Oh yes, we need cheaper science. What about cheaper wars?
2004 – 47 years after the beginning of the space exploration era
The next rovers were sent to Mars 7 years after Sojourner. They are famous Spirit and Opportunity.
So the time gap between missions gets shorter, and the science goals become more ambitions. If the earlier rovers were to test the Martian soil for its strength, abrasion and chemical compounds and Martian atmosphere, Mars Exploration Rovers (MERs) are equipped with instruments for searching for presence of water on Mars and also for determining the distribution and composition of minerals, rocks, and soils surrounding the landing sites.
On January 4, 2004, Spirit landed successfully in the Gusev crater – a site that appears to be a lake in the past. It was active from 2004 to 2010.
Opportunity landed on 25 January 2004 in Meridiani Planum -three weeks after Spirit. And it is still operates on Mars.
Both Spirit and Opportunity are 6-wheeled robotic rovers, powered by solar batteries. They dimensions are 1.5 m x 2.3 m x 1.6 m and their weighing is 180 kg.
For each rover, its six wheels are mounted on a rocker-bogie system where each wheel has its own motor. This allows rovers to move around a rough terrain. The rovers are able to reach the maximum speed of 0.18 km/h or 50mm/s with an average speed is about 10 mm/s.
The science payload includes 3 fixed science instruments and 5 instruments placed on the rover’s arm.
The scientific objectives of the Mars Exploration Rover mission are
- To find various proofs for a past water activity on Mars.
- To perform “ground truth” — calibration and validation — of surface observations made by Mars orbiter instruments and compare it with observations made by various instruments from orbit.
More about science objectives for MER can be found on the NASA web site.
In a table below I put together some information about rovers:
Below, I present this information in graphical format. I made a chart that shows how the rovers capacity grows from mission to mission and also provide graphical illustration for rovers’ sizes.
The figure and table above demonstrates good trend: the rovers’ weight and size are getting bigger from mission to mission and the weight of science payload also grows in line with rover weight. Thank you to new technologies! It also shows that for successful landings the mission operation time exceeds its planned time in a matter of an order (3000/90=33.3).
Returning back to Curiosity
The real success of previous MERs paved the road for Curiosity. It would be really good if Curiosity could provide the evidence of the presence of water on Mars in its past, and may be the presence of microbial life. However, this type of evidence is difficult to get. Even on Earth it is not easy to trace the presence of organics in old sediments and it takes a lot of complicated lab equipment to confirm results. And we should remember that actually the presence of complex organic molecules does not necessarily points to the presence of life.
But still, I appreciate the pace of Marcs exploration, the technology developments that made it possible and shift of science objectives, from just exploring the planet in 1971 to looking for life on it in 2012. It is impressive.
Watson, Traci (April 14, 2008). “Troubles parallel ambitions in NASA Mars project”. USA Today.
MSL fact sheet – http://marsprogram.jpl.nasa.gov/msl/news/pdfs/MSL_Fact_Sheet.pdf
Mars 3 – images – http://www.mentallandscape.com/C_CatalogMars.htm
V.G Perminov, “The Difficult Road to Mars”, 1999, NASA HQ, NP-1999-06-251-HQ, http://klabs.org/richcontent/Reports/mars/difficult_road_to_mars.pdf
Ted Stryk’s page on the Mars 3 Probe – http://www.strykfoto.org/mars3.htm
The scientific objectives of the Mars Exploration Rovers Spirit and Opportunity -http://marsrovers.nasa.gov/science/objectives.html
Sojourner page at JPL – http://mars.jpl.nasa.gov/MPF/roverpwr/power.html
“Special Issue: Spirit at Gusev Crater”. Science (5685): 737–900. 6 August 2004.
MER Press kit – http://marsrovers.jpl.nasa.gov/newsroom/merlaunch.pdf
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Amos, Jonathan (July 22, 2011). “Mars rover aims for deep crater“. BBC News. Retrieved 2011-07-22.
Sallé, B., Lacour, J., Mauchien, P., Fichet, P., Maurice, S., & Manhès, G. (2006). Comparative study of different methodologies for quantitative rock analysis by Laser-Induced Breakdown Spectroscopy in a simulated Martian atmosphere Spectrochimica Acta Part B: Atomic Spectroscopy, 61 (3), 301-313 DOI: 10.1016/j.sab.2006.02.003