This is an adapted Wikipedia article. (my comments in italics)

As a lifelong inventor and independent scientist, James Lovelock has created and developed many scientific instruments, some of which were designed for NASA in its program of planetary exploration. It was while working as a consultant for NASA that Lovelock developed the Gaia Hypothesis, for which he is most widely known. He also claims to have invented the microwave oven.

I can remember using a microwave device in 1961 as part of a research project I was involved in.

In early 1961, Lovelock was engaged by NASA to develop sensitive instruments for the analysis of extraterrestrial atmospheres and planetary surfaces. The Viking program, that visited Mars in the late 1970s, was motivated in part to determine whether Mars supported life, and many of the sensors and experiments that were ultimately deployed aimed to resolve this issue. During work on a preparing for this, Lovelock became interested in the composition of the Martian atmosphere, reasoning that many life forms on Mars would be obliged to make use of it (and, thus, alter it). However, the atmosphere was found to be in a stable condition close to its chemical equilibrium, with very little oxygen, methane, or hydrogen, but with an overwhelming abundance of carbon dioxide. To Lovelock, the stark contrast between the Martian atmosphere and chemically dynamic mixture of Earth’s atmosphere was strongly indicative of the absence of life on the planet.

He did some research and found out if you take the atmosphere of the Earth and let it achieve equilibrium … you get an atmosphere that is similar to that of Mars!!.

When the Viking probes were finally launched to Mars, they searched (unsuccessfully) for life. Interestingly(2016) they are still looking for life, particularly after water was discovered on Mars.

Water was the ‘home’ for the development of life on Earth

Lovelock invented the electron capture detector, which ultimately assisted in discoveries about the persistence of CFCs (Carbon Fluorine Compounds) and their role in stratospheric ozone depletion. 

Lovelock was elected a Fellow of the Royal Society (a prestigious institution) in 1974.

He is a well respected scientist.