Thread by @marsgeology, MARS ROVER MISSIONS! IMAGES OF MARS! ...a thread I have just [...]

MARS ROVER MISSIONS! IMAGES OF MARS!

...a thread

I have just uploaded my #LPSC2020 poster from my internship research with @esa last summer. I am so excited to be sharing this research so I wanted to talk a little bit about the Mars Sample Return mission I had the honour to be a small part of.
https://www.hou.usra.edu/meetings/lpsc2020/eposter/2042.pdf

I had the incredible opportunity to be a part of the Human and Robotic Exploration (HRE) team @esa working on the Sample Fetch Rover (SFR).
SFR's job is to collect the sample tubes filled with Martian regolith that @NASAPersevere deposits in Jezero crater. (Image by @esa)

Jezero crater was chosen as the landing site for MSR due to the presence of alluvial fans, indicative of past water flow. (Image NASA/JPL-Caltech/ASU)

I undertook a terrain analysis & traversability study of the proposed landing site at the beginning of the SFR Phase B. I categorised the terrain using @HiRISE images in @qgis software.

The safest terrain was smooth or fractured terrain, proven to be traversable from previous rover missions. The steepest rover climbs have also been on this terrain type. (Image by @HiRISE & NASA/JPL)

$The safest terrain was smooth or fractured terrain, proven to be traversable from previous rover missions. The steepest rover climbs have also been on this terrain type. (Image by @HiRISE & NASA/JPL)$

Purely from orbital analysis it is sometimes hard to differentiate smooth terrain from deep sand. @MarsRovers Spirit unfortunately discovered this at 'Troy', an area of what appeared to be smooth terrain from orbit. (Image by NASA/JPL)

Sand ripples were found all across the landing site and were the most variable terrain type to analyse. Ripple amplitude and substrate type (firm or sandy) are variables of determining rover traversability.

Some ripples are similar to those seen in previous rover traverses. Oppy's drive through ripples at Meridiani Planum was a success and the ripples appear to have similar characteristics in @HiRISE images.

Oppy appreciation tweet

(Image by NASA/JPL)

Larger, single ripples can be traversed if they are deemed necessary for the mission timeline success. The route around a large ripple can add many sols to a mission. Curiosity traversed Dingo Gap megaripple between sols 533-538. (Image @HiRISE)

Dingo Gap megaripple had a wavelength of ~7 m and amplitude of ~1 m. @MarsCuriosity did experience slip
- distance travelled is not as far as commanded - on the way up the ripple and skid - distance travelled is greater than distance commanded - on the way down. Images NASA/JPL

More hazardous sand ripples to traverse include polygonal ripples and Transverse Aeolian Ridges (TARs). These were found to be prolific in the south western edge of the proposed landing ellipse. (Images: @HiRISE)

Polygonal ripples were shown to be dangerous by Oppy's attempt at traverse through a ripple field on sol 446 of the mission. The rover's wheel sank adding 38 sols to the misson. (Image is a vertical NavCam projection by NASA/JPL, and is one of my favourite rover images)

In total, I classified 16 terrain types including smooth, fractured, rough, sandy and rocky terrains. Comparing @HiRISE images of Jezero to those of other Mars rover missions I was able to get a sense of what is likely to be traversable for SFR.

This research has highlighted that the physical properties of the Martian duricrust are a large factor in the safe or hazardous traverse of a rover.

Duricrust is a thin, cemented layer of regolith that behaves in a brittle manner and can be easily destroyed by low surface pressures e.g. a rover's traverse. For example, this image shows the duricrust being destroyed by Spirit's traverse at Home Plate. (Image: NASA/JPL)

The future of rover missions includes further use of autonomous driving capabilities. Orbital terrain classifications can highlight broad regions where autonomy can be used, but a more detailed analysis must be done from the ground. Image from Callas (2015).

Future missions are able to utilise the huge amount of data and images from previous missions to help ensure mission success. I have been so honoured to have been even a small part of this incredible mission.

Here is the link to my #LPSC2020 poster again that summarises this thread:

https://www.hou.usra.edu/meetings/lpsc2020/eposter/2042.pdf

'Traversability Study of Jezero Crater using Comparitive Orbital and Ground Based Image Analysis of MER and MSL Rover Traverses'

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