The aliens have landed on my back lawn

Or, be careful what you do with that very useful silicone spray.

A couple of weeks ago I looked out onto our rain-sodden back lawn, which I have carefully tended since its third (or fourth) incarnation of several years ago. And I saw this very strange pattern developing on the grass. It was much less defined at the time.

The days passed, puddles came and went, and as the pattern became clearer I realised what it must be.
I like a weed-free lawn, you see.
I have spent hours pulling all of the little bits of seedy annual grass that somehow managed to survive the doses of RoundUp that obliterated the last lawn. I frequently scrutinize the area for baby clover plants or wee dandelions that might have the nerve to rear their heads among the blades of grass.
I prefer to hand pull the few weeds that find a spot to thrive in my garden, which has become an easier principle to hold since we decided to cover the flower and veggie beds with tree shreds. But once in a while, like at the beginning of fall when weeding has lost its novelty, I do a judicious spray with some weedkiller. We have just discovered the joys of silicone spray, since the WD40 lost its little straw and Jeff said wereallyneedsomenewWD40, pleaseohpleasecanwegetsome? Because you know that my frugal self just wanted to find a way to make the old stuff work. But I relented and we trotted off to Ace Hardware and when we saw the canister of silicone spray sitting on the shelf next to the other humbler oil-based lubricants, I had to have it. And it proved to be a miracle worker and we use it on everything we can think of.
Fast forward to The Day I Decided to Kill Weeds. For some reason, our garden spray canisters don't seem to last anywhere near as long as they should, so I was down to one little inefficient canister. I added the poison and started to push the handle up and down to create some air pressure, but the action was very sticky.  Then I had a light bulb moment.
Silicone!
So I sprayed the shaft with silicone and commenced pumping on the slabs of stone next to the greenhouse. That baby was slick and I was in the middle of congratulating myself on the forethought to buy that lovely silicone spray when all of a sudden, WHOOSH! The canister exploded, sending poisonous water all over the rocks and yours truly.
If I ever get cancer I will blame it on this event.
It may have gotten up my nose.
But at least, I thought to myself, it didn't get on any plants or the lawn.
Or did it?

And on that rainy day, I realised that the exploding spray had indeed reached the lawn. And apparently there had been enough of it to attach itself to the soles of my shoes and now there are alien footprints all over my lawn.