Misleading headline again (this is a pattern), they are not visible from space, they can be estimated based on satellite images using a complex model. That's not at all what common people understand by "visible".
Much like a human brain estimates or imagines an image based on a complex model transformation of sensor data from various cones arrayed within the eyes.
Here we have a straightforward, readily pipelined, multispectral transformation that combines 'colours' from the non (human) visible part of the greater spectrum and creates a shifted blended colour image in the human eye visible part of the spectrum such that target vegetation is prominent.
In the remote sensing domain calling such things visible has been common parlance for three decades.
It's similar to that trope scene in action films that has a sniper using a thermal filter to enhance body heat for better target imaging.