Mission update (29 July) - rounded grains from impacts or eruptions

Despite their superficial similarity to Opportunity’s “blueberries”, the spherules at “Rowsell Hill” have a very different composition and likely origin. In Meridiani Planum, the spherules were composed of the mineral hematite and were interpreted to have formed in groundwater-saturated sediments in Mars’ distant past. By comparison, the spherules in “Rowsell Hill” have a basaltic composition and likely formed during a meteoroid impact or volcanic eruption. When a meteoroid crashes into the surface of Mars, it can melt rock and send molten droplets spraying into the air. Those droplets can then rapidly cool, solidifying into spherules that rain down on the surrounding area. Alternatively, the spherules may have formed from molten lava during a volcanic eruption.

Impacts and eruptions... both violent events. Neither exactly what Percy was sent to look for, you'd think - namely evidence of water action, and possibly traces of biology.

Except that there's a very important difference between the two: impacts are common everywhere, from Mercury to Pluto, and provide no proof that a planet has a geologic "pulse", that its insides are warm and active. Whereas volcanic eruptions prove exactly that. If we had these spherules in hand, we could determine their age and know that this part of Mars was still active at that date. Put that information about Mars' internal heat together with the dates of the old lake sediment we sampled inside Jezero Crater, and you've got yourself a story.

You don't get this sort of information by landing in the middle of the plains, as the Chinese sample return mission and the SpaceX proposal would have it. Just saying.

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Despite their superficial similarity to Opportunity’s “blueberries”, the spherules at “Rowsell Hill” have a very different composition and likely origin. In Meridiani Planum, the spherules were composed of the mineral hematite and were interpreted to have formed in groundwater-saturated sediments in Mars’ distant past. By comparison, the spherules in “Rowsell Hill” have a basaltic composition and likely formed during a meteoroid impact or volcanic eruption. When a meteoroid crashes into the surface of Mars, it can melt rock and send molten droplets spraying into the air. Those droplets can then rapidly cool, solidifying into spherules that rain down on the surrounding area. Alternatively, the spherules may have formed from molten lava during a volcanic eruption.
Impacts and eruptions... both violent events. Neither exactly what Percy was sent to look for, you'd think - namely evidence of water action, and possibly traces of biology.
Except that there's a very important difference between the two: impacts are common everywhere, from Mercury to Pluto, and provide no proof that a planet has a geologic "pulse", that its insides are warm and active. Whereas volcanic eruptions prove exactly that. If we had these spherules in hand, we could determine their age and know that this part of Mars was still active at that date. Put that information about Mars' internal heat together with the dates of the old lake sediment we sampled inside Jezero Crater, and you've got yourself a story.
You don't get this sort of information by landing in the middle of the plains, as the Chinese sample return mission and the SpaceX proposal would have it. Just saying.