Kurt Schwehr 5/17/93 schwehr _at_ cs stanford edu Revised 8/19/93

2.2.2.3 Precursor Rover Mission Options

2.2.2.3.1 Goal

This section describes two missions that fit the 1998 and 2000 launch windows to Mars which currently have no schedualed flights. They could provide continuity to the Mars exploration plan. The second mission works well with the SIMM precursor missions in that it provides much needed context for the human surface exploration. These two options are meant only as a small sampling of what could be done within these two launch windows using existing technology. All of the landing site numbers mentioned refer to the Mars Landing Site Catalog (Ref. Greeley, 1990).

2.2.2.3.2 Rover system, assumptions, and constraints

The rover that looks the most attractive for these missions is the Russian Marsokhod described in Appendix A.1. It should be outfitted with a laser-rangefinder, mass spectrometer, core drill, panoramic camera with zoom, ground penetrating radar, and basic meterology instruments. Several of the missions will substituted/add instruments to suit the objectives. The first two rovers are sent on the highest priority missions so that if one of the first two rovers should fail, one of the next two rovers can be retargeted to replace the damaged rover. The lander should be equiped with a decent imager to give the best context to the rover mission and allow for improvements in the mission plan. Once down, the lander should deploy a seismometer to add to the global network started by the NASA MESUR and ESA MARSNET missions. None of these missions are meant to be sample returns due to cost considerations. During each launch window, two Marsokhods will be launched on a Proton or similarly capable launch vehicle.

2.2.2.3.3 Option A - General Science

The goal of this mission set is to gain a wide spectrum of knowledge about very different sites scattered about the planet.

2.2.2.3.3.1 1998 Launch Window

These two rovers are targeted for sites in the southern hemisphere of Mars.

2.2.2.3.3.1.1 Biological Mission

The target for this exobiology mission is a high latitude permafrost/ground ice area. The exact site is to be determined by Mars Observer imaging. The ideal site would be above 70 degrees South latitude in a area of a paleo-lake. The reason for choosing the southern hemisphere is due to the Northern lowlands being much younger - probably only one or two billion years old. The processes that created the lowlands probably destroyed signs of previous life.

2.2.2.3.3.1.2 Sedimentology and volcanology mission

This mission is to a small channel named Dao Valles in Hadriaca Patera. The canyon is approximately 200km long. The site area is listed as site #32 and is near sites #49, #62, and #80 (Ref. Greeley, 1990). The rover should land near the top of the canyon and progress down the valley. It is assumed to be easier to travel down a surface that it is to go up. For example, sliding down is often possible where a vehicle in not able to climb.

2.2.2.3.3.2 2000 Launch Window

2.2.2.3.3.2.1 Volcanology mission

The target is a small volcano named Uranius Tholus. It is an older volcano located on the Tharsus Bulge at 26N 97W. The rover is to land near the base of the volcano and traverse towards the caldera. The smaller size of the volcano allows the rover to traverse a larger number of volcanic facies within its mission range. A rover around Olympus Mons for example would not be able to get close to more than three or four features since they are so large compared to the 100 km range of the rover.

The landing site is 10 to 20 km West of Uranius Tholus at an elevation of about 4500 meters. The vehicle will then traverse East, upwards to the caldera. The highest elevation of the edge of the caldera is at approximately 8500m.

2.2.2.3.3.2.2 Backup/Opportunity mission

If the backup and oppertunity missions are not needed, this rover could be sent to one of many interesting sites: Olympus Mons (sites number 28 and 36) or Elysium Mons (site 40) both of which are young volcanoes, or a major impact crater.

2.2.2.3.4 Option B - Human precursor

The largest valley system is Valles Marineris. It contains Candor Chasma which is the proposed primary landing site for SIMM's first manned landing. Carr (1981) described Valles Marineris from the Viking missions data:

"Just south of the equator... are several enormous, interconnected canyons, which have been collectively called Valles Marineris. They extend roughly east-west for over 4,000 km, from the summit of the Tharsis bulge at Noctis Labyrinthus, down the crest of a broad rise on the eastern flank of the bulge, to some low-lying areas of chaotic terrain between Chryse Planitia and Margritifer Sinus. Individual canyons may be over 200 km wide and 7 km deep. In the central section, where there are three partly connected parallel canyons, the entire system is over 700 km across. ... The canyons are poorly graded and are commonly choked with landslide debris, and most of them lack indications of fluvial action on their floors [that are seen in the channels.] Many sections are segmented and consist of strings of closed depressions rather than a continuous canyon."

"The canyons can be divided into three sections: a complex maze of interconnected canyons-- the Noctis Labyrinthus--at the west; the main section of roughly east-west-trending canyons in the center; and some irregular depressions which merge with the chaotic terrain further east... The main canyon extends... a distance of 2,400 km. Along this entire length the canyon... consist[s] of parallel canyons and chains of craters and graben... The canyons are widest and deepest in the central section... where three huge parallel troughs are each close to 200 km across... [In t]he two northernmost troughs, the Ophir and Candor Chasmas... layered sequences, suggestive of cyclic sedimentation, are most common."

"[To the East,] the canyons consist of two main depressions, the relatively narrow Ganges Chasma to the north and a broad depression including the Eos and Capri Chasmas to the south. Both depressions continue eastward into irregular areas of chaotic terrain."

"Faulting [related to the Tharsis bulge] appears to have played a key role in formation of the canyons... The [data] suggest that faulting and erosion proceeded simultaneously rather than succeeding each other, because erosional features, which could not have formed until after faulting started, are themselves cut by faults."

"In summary, many of the characteristic of the canyon can plausibly be explained by faulting, mass wasting, and the effects of groundwater. We are left, however, with two major unsolved problems: the origin of the layered sediments in the central section and the fate of the materials excavated to create the enormous void that the canyons represent."

Obviously, we do not know very much about Valles Marineris. If we intend to send astronauts to Candor Chasma for field exploration, we should have as detailed knowledge as possible of the area surrounding the field study area. Geology is much better understood when it is placed into regional context. This is analogous to scientists strong desire to see over the horizon at the two Viking landing sites.

2.2.2.3.4.1 1998 Launch

This launch focusses on areas that are primary targets for human missions to Mars.

2.2.2.3.4.1.1 Candor Chasma

Candor Chasma is the proposed landing site for the SIMM human landing. Therefore this is the most critical site to survey. The Mars Landing Site Catalogue(1990) has sites number 22, 43, 54, 72 in this area. Carr suggested a penetrator mission for site #72 which is between Ophir and Candor Chasmas. Site 22 is located on Candor Mensa, a mesa within Candor Chasma. Site #'s 43 and 54 are both within Candor Chasma with 43 being to the south.

2.2.2.3.4.1.2 Melas Chasma

Melas Chasma is directly sourth of Candor Chasma and is in the main portion of Valles Marineris. It will most likely be out of range of the first astronaut group, but is location that may be site the astronauts on future missions explore.

2.2.2.3.4.2 2000 Launch

2.2.2.3.4.2.1 Noctis Labyrithus

This is the chaotic zone that is at the top of Valleys marinares. It is the probable source of the massive amount of water that carved out this massive valley. This is the highest risk mission of the set that will probably result in early destruction of the rover. Never the less, it is of extreme imporance in understanding the martian fluvial envornment. The rover should land about 50 km away for the start of the chaotic terain. It should then proceed as far as possible into the chaotic zone.

2.2.2.3.4.2.2 Capri Chasma/Eos Chasma

Capri and Eos Chasmas are at the far eastern end of Valles Marineris and are listed as site number 74.
Kurt Schwehr / schwehr _at_ cs stanford edu