Mastodons, Missing Ancestors, and The Rings Of Saturn

This week,  the discovery of some very old (130,000 years) Mastodon remains which appear to indicate that humans occupied North America much earlier than previously thought.
The discovery indicates that a group of human ancestors reached North America where the Mastodon remains were found, over 100 000 years before the accepted date; it is obvious that the creature was 'processed' using tools, as opposed to being devoured by carnivores.
However, there is no trace of any civilisation in the area.
So who were they ?
Where did they come from?
And why just leave a single mastodon, then vanish ?

Fossil mastodon bone                                    San Diego Natural History Museum

This thread led me to a piece which reminds me that all fossilised human remains discovered worldwide thus far could be carried in a small pick - up truck.
Which gives an idea of the problem
Without any further evidence, we may never know.
It's a tantalising tale that will interest palaeontologists / anthropologists for years to come.
My further attempts to research the prehistory of the Otay Mesa brought me to a piece on the recent discovery of a fossilised mastodon and a whale - showing how dramatically the area changed over time.
I then looked at some vague maps of the area, but ended up reading of how yellow go - cars can be used to explore San Diego.
Returning to thoughts of the original find , I wondered how such a random discovery could be used as evidence of no further civilisation.
Did they dig up the whole area ?
When the fossils were discovered, did they halt construction of Route 54 to expand the search ?
No.
Which is sad, but it's fairly well known that there was no developed architecture at that time - and it's almost certain that these hominids were nomadic.
Don't forget that this was an era marked by mini-ice ages and changing sea levels.
It's almost certainly the case that any further evidence is now elsewhere.
We'll probably never know who they were.
Despite the excitement, without digging up huge swathes of land around route 54, there is still a huge gap of time between our mysterious ancient mastodon hunters and human settlers.

Meanwhile, in space...

Leaving behind the ancient history of Earth, we discover that scientists at the university of Arizona are developing a large ' polytunnel' , specifically geared towards growing crops on Mars.
Simultaneously, experiments have shown that martian soil can be compressed into bricks, and may provide a realistic building material , without costly consignments being shipped from Earth

Cygnus approaches ISS, image by Thomas Pesquet                      NASA / ESA

The above image left me stunned when I saw it earlier this week,with the approaching Cygnus craft looking small and insignificant against the majestic backdrop of Earth.

Meanwhile, above Saturn...

Cassini has begun its final manoeuvres, executing 22 dives through the rings of Saturn .
 Images are already reaching us,showing close ups of the gas giant, and its moons.