“TANGO DELTA nominal”
“RIMU stable”
“UHF strong”
“TOUCHDOWN CONFIRMED”
And with those last few words, NASA landed the Mars Rover Perceverance on Mars.
For some of you this might be the first major “off earth” exploration but for some of us more senior to you we can still remember that “FIRST STEP FOR MANKIND” broadcast that started man's physical exploration of the moon.
So, why are we exploring the cosmos? It's man's desire to know more about where we came from and possibly who might also be out there. “But there's nothing there!” can be said when Mars is compared to Earth, which is mostly true. There appears to be no trees or vegitation, maybe no animals large and small, maybe no microfawna but were they there in the past? How do we figure that out, with geology!
Wikipedia defines geology as:
“An Earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon.” Well, that certainly brings this exploration to the forefront!
That's well and good you might say but how can we study a place or event so far away? We must first study our planet Earth and it's processes and then, it is hoped, that we can extrapolate these findings and apply them to places we can not directly visit.
So, lets have a quick look at where Perceverance landed. The NASA scientists sellected the Jezero Crater area in 2007 because of it's unique characteristics having them believe the area was once flooded with water and was home to an ancient river delta! The leveling effect of a large lake made the area appear flat enough for a successful landing and then exploration by Perceverance could be done on the flat bottom and over to the sloping rim of the crater or the bank of the lake.
[Image: JEZERO CRATER DELTA MAP]
On the TV there is a show that uses animation to “drain the lakes” or water bodies to study what might be found once not hidden by the water. In most cases they are looking for ancient sunken ship wrecks or submarines but what they also do is expose the shore lines and bottom countours for interpretation of geological events that are occurring or have occured. Below is a rendition of what the Jexero Crater would look like if it was still a lake.
[Image: JEZERO CRATER RENDITION IF FULL OF WATER]
These geological lake events are referred to as “eutrophication”, the aging over geological time and changes in a lake from having a lower level of primary productivity to a higher level of productivity. These changes can be simplified by observing a lake that is deep but then slowly fills with clay sediment to form a slough or, one of clear water to one that has an abundance of suspended particles that clouds the water to look muddy. Unfortunately, the Jezero Crater lake has now vanished so what is there to interpretate? Why, the bottom contours and shapes are still there.
If you had a basin full of water and suddenly cut a knotch in it's side, the water would rush out and cut a fairly straight river course. As the basin emptied and the flow diminished, you would notice the water start to slow and then meander. As it slowes the particles (large and small) washed down by the water begin to settle on the bottom forming gravel and clay layers. This fills some meanders and forms new ones and developes what is referred to as a “delta” where the water fans out into the country side. It's these characteristic fan shaped deltas that caught the investigative eye of the scientists and which they observed in this crater.
Productivity of a lake or the growth of suspended plant and animal life at first allows light through and the water appears clear but later with more organism living in the water it turns greenish or brown or dirty. As these organisms die, they settle to the bottom, filling in the lake. With the Jezero Crater lake now gone, it is hoped that the old lake bottom of the delta will hold evidence of these past organisms with gravel and clay layers for sampling.
This Earth Cache is located on Lake Drive West road of Dauphin Beach on the south edge of Lake Dauphin. This lake has one exit river but over 5 rivers and various stream and drains emptying into it. With all this inflow of sediments, the lake eutrophication has been greatly increased. As a result, the characteristic delta fans are very obvious here without “draining the lake” as it were. The image below is of Edward's Creek Drain flowing into Lake Dauphin just northwest of the Earth Cache location. Do you see the “fan” opening into the lake?
[Image: EDWARD'S CREEK DRAIN INTO LAKE DAUPHIN]
Now lets imagine the Lake Dauphin delta with the water removed to show the fan and then look at a NASA crater image of Jezero with the water removed, do you see the “fan” here? If your unsure, look at the first crater image for the area labelled as the “delta”.
[Image: JEZERO CRATER DELTA AS VIEWED TODAY]
From this apparent delta image you can see what appears to be the sediments from the river and how they have been distributed out onto the flats. It's these geological features that the Rover “Perseverance” is going to investigate and sample, looking for evidence of past life and geological processes as evidence for past water on Mars.
To get credit for this Earth Cache, log it and then separately message the cache owner through geocaching messenger the answers to the following questions. If there are any concerns with your answers, the CO will contact you in reply.
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As you stand here on the shore of Lake Dauphin, how are the beaches of the cabins east of the cache location different from those west of this location? You can check out these beach areas by accessing them utilizing “Public Access” points, to the east at N51 8.696 W99 50.488 and to the west at N51 8.901 W99 50.805. Think in terms of eutrophication.
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What other features on Mars' images above show a possible wet past?
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What are used to control beach erosion at the cache location?