Perseverance was sent to Jezuro Crater because it contains a river delta that may have captured and preserved microorganisms if Mars ever had life. So what happens if it doesn't have the right kind of rocks on this episode of Mars guy? The Mississippi River has produced the seventh largest delta deposit on Earth and people living on it produced one of the original forms of blues music. Like delta deposits all over the world, they usually are filled with clay minerals that make up mud. Those clay minerals are really good at absorbing organic matter from dead microbes and preserving it over geologic timescales when the mud turns to stone. This is the big picture reason why it makes sense to send a rover to collect samples from a delta on Mars, the microbes part, not the blues part. Mars first arrived at the Jezuro delta in late April of 2022 and it spent most of its time exploring and sampling the lowest parts of the deposit. This is where it found the most promising rocks in the search for Martian microbes. Three locations contain rocks that are very fine grained, either mudstones or siltstones, so better for microbial preservation potential. But a bit higher up the delta just above the feature in formerly named the Bacon strip, the rocks of the cliff known as Rocky Top are different. Here's Mars Geiferscale. These rocks are much coarser grained sandstones, nicely shown in this comparison with the abrasion spot on a rock from the Bacon strip. Perseverance has now visited the top of Rocky Top, which by the way is named after a feature in one of Earth's National Parks, as are all the locations visited by Perseverance. And note that I did say that the Bacon strip was named informally. Here's the view out across the surface at the same level as Rocky Top. Perseverance deployed its arm on one of these rocks and started with its gas dust removal tool, which may be the first time this was done before an abrasion operation. And yes, Perseverance does have a tool for removing dust, but it won't be using it for cleaning solar panels because it doesn't have any. And no, it's not likely to be used on ingenuity solar panel because the two vehicles don't ever meet up, and ingenuity seems to be doing just fine on its own. See the previous episode. It's clear from the various images acquired by the mast and arm mounted cameras that Rocky Top could perhaps be named gravel top, given the size of some of the grains it contains. And you don't have to be a geologist to know that gravel is not mud. So these deposits likely were laid down by fast flowing water, not a lazy river, which is not ideal for accumulating clay-rich mud and the tiny Martians we hope to discover. The layers higher up are filled with rounded cobbles and boulders, a sure sign of floodwaters raging across the top of the delta as it built up out of the lake. Those rocks provide clear evidence that the Jezero Delta is more accurately identified as a fan delta. As nicely described by Brian Ricketts on his Geological Digressions website, fan delta's are like alluvial fans, except they dip their toes in lakes and shallow seas. And the folks at Wikipedia describe an alluvial fan as an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. So perseverance is climbed up from what likely was the floor of ancient lake Jezero, home to mudstones and siltstones, and onto an alluvial fan that was above water. But its next destination is curvilinear features that may have formed as point bars in a meandering stream or river, just like those formed by the Mississippi River and known to contain mud. So it's too soon to sing the blues for the Jezero Delta.