Are you finding the Delhi air a little smoggier than usual? Smog isn't unusual to Delhi in the winter, but a satellite has confirmed again that one of the big causes of it is still very much active.

The Visible Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this image on 30 October:

And what does this image mean?

According to NASA, the red outlines are spots where the sensor detected surface temperatures that are associated with fires. The agency while releasing the image said that "thick plumes of smoke" were emerging from the hot spots. Most of these spots are in Punjab.

The smoke from these fires has been found to contain toxic chemicals like carbon monoxide, nitrogen oxides, and toxic particulate matter - none of which is good news for those breathing it.

So what's causing the fires?

Burning of crop stubble (the remains of the plant after the grain has been removed) by farmers. This is mostly done to clear fields before the next sowing season begins in November.

Turns out this had been declared illegal years ago and authorities have been trying to get farmers to stop it. But if the NASA satellite image is anything to go by, it hasn't worked this year.

Ironically enough it's in the farmers interests to stop burning the crop stubble, because, as this expert pointed out to DNA, it affects the fertility of the soil as well. It's no good for the farmers' health either given they're breathing that smoke as well.

The Punjab government has, aas this Times of India report points out, provided , provided subsidies for machines like shredders so that farmers can get rid of the stubble and use it for other purposes like making organic fertiliser.

But evidently, it's still cheaper for farmers to burn stubble. And since authorities are reluctant to take action against them, you might just find it a little harder to breathe in Delhi in the coming days.