Your hair is like a travel journal. According to scientists at the University of Utah, it can reveal the regions where you drank water. And so it can be used to determine where murder victims lived prior to death – and possibly to test the alibis of suspects who claim no connection to the crime scene.

Rainwater, the source of drinking water, is made up of hydrogen and oxygen. These two elements exist in forms called isotopes, which vary slightly in weight. As rainclouds move inland from the coast the heavier-isotope raindrops fall first. By comparing the chopped locks in barbers’ shops with local water samples in 65 cities across 18 American states, Professor Thure Cerling and Professor Jim Ehleringer produced colour-coded maps showing how water changed across the country. They published their work last month in the Proceedings of the National Academy of Sciences and have set up a company, IsoForensics, to commercialise the research, which is already being used in Utah to help to identify dead bodies.

— During the next few weeks a spacecraft called Ulysses will freeze to death after spending 17 years pirouetting about the Sun’s poles. It is the end of an era – not only for the spacecraft but also for me. Back in 1990 I was one of the first graduate students to look at the astonishing data that Ulysses sent back describing, in seemingly infinite strings of numbers, the invisible magnetic shroud thrown by the Sun over the Solar System. Ulysses’s planned five-year odyssey overran by a dozen productive years, teaching us about solar storms, space weather and interstellar dust. Richard Marsden, who managed the craft for the European Space Agency, has saluted this “terrific old workhorse”.

Its six-year orbit takes it from the solar poles out to Jupiter, to which it is currently voyaging. As it leaves the Sun behind, its temperature drops. If Ulysses becomes colder than 2C its hydrazine fuel will freeze. The power generated by the decay of onboard plutonium will soon fall below the level needed to work the onboard heaters. At that point mission control will no longer be able to contact it and a shivering Ulysses will be consigned to a never-ending, lonely orbit.

— It is also time for this old workhorse to bid farewell. As of this week I am on maternity leave. Before I go, however, I would like to thank the many of you who write, e-mail and post comments online in response to my musings, and to apologise to the (hopefully) few who do not receive a reply. I am proud of having such erudite and feisty regulars as the woman who recently took me to task for my scepticism about complementary medicine. Despite my failings, she wrote, she would continue to read me “because mostly you sound a sensible young woman and I am glad The Times employs you”.

Me too. I look forward to taking up my pen again towards the end of the year.

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