Mars Exploration Rover Landing Site Memorandum

November 5, 2001

To: MER Project MEP and Landing Site Steering Committee

From: M. Golombek

Re: MER Landing Sites Ellipses

The next number of e-mails from me include jpgs [see "site parameters"section for these maps] of the 6 landing site ellipses for MER under consideration for final selection in April 2002. Two of these ellipses remain unchanged: Melas and Eos. The other 4 ellipses have been moved for safety and/or science reasons. The placement of the ellipses has included discussion between the science spokesperson of each site as well as project and Athena science team personnel. The ellipses have been transmitted to Mike Malin for MOC imaging when possible.

There are 4 top ellipses (Hematite, Melas Chasma, Gusev crater and Athabasca Vallis) and 2 backups (Isidis and Eos Chasma). However because of possible concerns at 3 of the top 4 sites, we have requested ROTO images of the top 4 and one of the backups (Isidis).

The ellipse center locations, sizes and orientations are included at the end of this e-mail. I have also included a general elevation of the site near the center of the ellipse.

Changes to the ellipses are as follows:

Hematite
TM20B and TM10A are the prime site for ROTO imaging. Because the latest ellipses are smaller than previous ones, we evaluated moving TM19B south because windows into the older terrain appeared more abundant. This ellipse had areas that did not have the hematite signature, so TM20B was retained as the prime because it is wholly in the hematite deposit. We moved TM20B and TM10A ellipse pairs to the same center so that MOC coverage will apply equally to both.

Athabasca Vallis:
The clear scientific and safety preference was for the southern of the ellipses considered. However, because we have the least MOC coverage of this site, we are requesting MOC imaging of a broader area before a final ellipse is selected. The provisional ellipse and the area requested for MOC images are shown in the image.

Gusev crater
We found a correlation between the etched looking terrain to the east of Thyra crater and very high MOLA pulse spreads indicating rough terrain. The ellipse has been shifted to the west and avoids all high pulse spread terrain and in existing MOC images appears smooth. The existing ellipse carries substantial MOC coverage in the eastern portion of the ellipse and so we have requested images initially in the unimaged portions of the ellipse towards the center and west.

Isidis
Rough looking terrain in MOC images in IP98B and IP85A correlates with higher 1 km scale slopes and higher MOLA pulse spreads. IP84A and IP96B appear smoother in both the MOC images and in the calculated slopes and MOLA pulse spread. These ellipses have been moved slightly south of the previous ellipse to avoid the cones that were near the north central part of the previous ellipses and to increase the likelihood of accessing ancient Noachian material shed off the highlands to the south. Because the ellipses have not moved very far south, a fair amount of MOC coverage still exists within them. In addition all the ellipses are centered at the same location so the same MOC images should apply to almost all of them.