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Tianwen-1 At Mars
serpens
post Jul 2 2022, 09:43 AM
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To me it looks like erosion of an armored dune, or more like a large ripple; effectively a blowout. As erosion progressed, armoring pebbles rolled down the slope
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rlorenz
post Jul 2 2022, 01:51 PM
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QUOTE (serpens @ Jul 2 2022, 05:43 AM) *
To me it looks like erosion of an armored dune, or more like a large ripple; effectively a blowout. As erosion progressed, armoring pebbles rolled down the slope


Yes, I'm inclined to agree. Very interesting locale! There are aspects that remind me of the yardangs in the Argentine Puna (where there are also gravel ripples) but I dont think I've seen rock tracks like this on a ripple.

It doesnt look like there is a lot of slope to drive motion, so presumably the rolling pebbles are wind-driven (or just possibly they roll when wind undercuts the sand from underneath). But if the sand can move, how are the trails preserved ? I dont doubt some modeler could come up with a scenario, but it would take a bit of fine-tuning for sand to be scoured in the lee of a pebble but not elsewhere...

It definitely looks like an armored dune overall, maybe an ejecta layer from a nearby impact covered the dune, immobilizing it, and then as you say, once the wind gets in it undercuts and blows out parts

Ralph
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Bill Harris
post Jul 8 2022, 06:09 PM
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Likely explanation, rlorenz. The Racetrack playa was a humorous stretch prompted by the low slope of this area. Clearly this is a wind-driven process, but how are sub-centimeter, millimeter-sized pebbles leaving such well defined trails?
Mars never ceases to amaze.

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Phil Stooke
post Jul 8 2022, 07:27 PM
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How about an alternative to the wind? A crater forms some distance away, ejecting a block which impacts at low velocity near this location, making a secondary crater. The low velocity of the secondary crater's own ejecta results in a spray of small fragments which fall on the surface, having enough momentum to roll or skid along the surface briefly to create the observed effect. Finer material in that little ejecta cloud is slowed by the atmosphere and falls elsewhere. If this sounds a bit ad hoc, fair enough, but this process must occur frequently all over Mars. Think of just throwing a handful of gravel over the ground and what that would look like.

Phil


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Huguet
post Jul 8 2022, 11:01 PM
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One thing for shure....

Zhurong Team from casc/csna... where are the close pictures of these moving material? .... we would love to see it...


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Hungry4info
post Jul 9 2022, 12:33 AM
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This is the thread for the orbiter, isn't it? Perhaps some of these posts should go to the Zhurong rover thread.


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nprev
post Jul 9 2022, 08:27 AM
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ADMIN MODE: Noted. The discussion here evolved a bit from landforms observed from orbit to same observed by the rover, but if the focus remains on the latter & these apparent 'roving pebbles' then it'll be moved over to the Zhurong thread. Fascinating stuff regardless. smile.gif


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Hungry4info
post Jul 23 2022, 05:24 AM
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Tianwen-1 has snapped a pic of Phobos.
(source here)
Attached thumbnail(s)
Attached Image
 


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Phil Stooke
post Mar 5 2023, 08:31 AM
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http://jdse.bit.edu.cn/sktcxb/cn/article/d....2096-9287.2023.

This is a link to China's Journal of Deep Space Exploration, and a notice of a forthcoming paper on Phobos observations by the TW-1 orbiter. There is an English language summary with interesting details. It will probably be another 3 or 4 months before the actual paper is released. More observations than the one shown above have already been made.

summary:

-----------------------------------
Orbit Design and Analysis of the Phobos Close Approach Exploration Mission for Tianwen-1 Mars Orbiter

ZHENG Huixin1, 2 , , XIE Pan1, 2 , , Li Haiyang1, 2 , ZHU Xinbo1, 2
1. Shanghai Institute of Satellite Engineering, Shanghai 201109, China

2. Shanghai Key Laboratory of Deep Space Exploration Technology, Shanghai 201109, China

Abstract: In this paper, the mission orbit design and analysis of a potential extended mission, Phobos close approach exploration, is carried out. The state at the end of the main mission is used as the input of the extended mission in this paper. Through analysis, it is concluded that Mars perturbation force can be used to adjust the argument of perigee, and the intersection frequency is related to the value of semi-major axis and eccentricity. Orbit descent maneuver should be performed to increase the number of intersections. As a result, the possibility of conducting aerobraking in order to reduce fuel consumption is analyzed. Finally, phase adjustment maneuver is calculated to complete the Phobos Close Approach Exploration Mission. The orbit design results and the velocity increment are given by simulation. The results of this paper can provide reference for the orbit design of Tianwen-1 orbiter extended missions.
Key words: Phobos close approach exploration / Orbit design / Tianwen-1 Mars Orbiter

Highlights
- Under the condition that the remaining fuel of Tianwen-1 Mars Orbiter is considerably limited and the Orbiter cannot be directly transferred to the orbit of Phobos, this paper utilized Mars perturbation force in adjusting the argument of perigee to make the orbit of the orbiter intersect with the orbit of Phobos.
- The intersecting frequency between the orbit of Tianwen-1 Mars Orbiter and Phobos is related to the value of semi-major axis and eccentricity. The intersecting frequency can be maximized by designing appropriate orbital parameters.
- In order to complete the close approach detection of Phobos, the Orbiter has to maneuver from the remote sensing orbit to the extended mission orbit. The Mars aerobraking is adopted as the orbital descent maneuver strategy, which can reduce fuel consumption by 80%.
- By designing an appropriate phase adjustment orbit period, the phase adjustment velocity increment can be controlled within 10m/s under the worst conditions of approach detection phase.
-----------------------------------

Phil


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Phil Stooke
post Mar 6 2023, 08:37 AM
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Guo, X., Yan, J.G., Yang, X., Liu, L., Chen, Y.H., Ye, M. and Barriot, J.P., 2023. Simulation of Phobos gravity field estimation from Tianwen-1 flybys and implications for the modeling of Phobos’ internal structure. Monthly Notices of the Royal Astronomical Society.


This citation is to a paper on Phobos flybys. It deals with simulations but again shows considerable interest in the exploration of Phobos.

Phil


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Phil Stooke
post Apr 24 2023, 07:21 AM
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https://twitter.com/CNSAWatcher/status/1650374776534474754

This tweet has links to a nice Tianwen-1 global Mars map in several different projections.

Phil


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kymani76
post Apr 24 2023, 08:28 PM
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Attached Image

Some synthetic views from low resolution version of TW1 map, with poles visible.
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Phil Stooke
post Jul 11 2023, 03:34 AM
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Orbiter selfie apparently taken by a deployable camera:

https://twitter.com/AJ_FI/status/1678438370291113986


Phil


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