Professor Pillinger was diagnosed with MS in 2005
Colin Pillinger, the professor of planetary science who was the lead investigator on the Beagle mission to Mars, explains why he finds the debate around assisted suicide generated by fellow MS sufferer Debbie Purdy "deeply depressing".
"It's just so negative, and it's time to speak out. Basically all anyone hears about multiple sclerosis comes from this one woman.
"It's entirely the wrong message, and everyone comes away with the impression that there are all these people with progressive, incurable diseases just sitting at home waiting to hear if they can go to Switzerland to die.
"It's not like that - there are plenty of us out there with these kind of conditions who want to live and who want to carry on doing what we do - whether it's science or sitting in the garden.
"Our lives are not miserable, but you wouldn't know that from the coverage."
Just one story
"The other problem is that rather than talking about funding and finding a cure for the disease, we're talking about dying. The government can say - this is what you wanted, and we've delivered, and now you want £50m for research?
"My daughter has just taken part in the Ironman event to raise money for MS. It would be so sad if we got to a situation where people are dissuaded from fundraising because of all this negative coverage.
"Moreover all this has been completely unnecessary. There is a perfectly adequate legal way to test this, her husband could have just taken the risk. No-one has been prosecuted so far.
"This is a debate that has been dominated by one woman and her story. It's time now for something positive.
"We should look to Terry Pratchett and the way he has spoken about Alzheimer's.
"We should be talking about how to live, not how to die."