What's wrong with my carrot? 

I was picking carrots today and discovered that the top of this one was covered in what I'm pretty sure are aphids. I have never experienced this before, and it was only on one carrot which was interesting. The carrot itself and the leaves were fine. 

So...

Are they aphids? What causes them? What can I do to prevent them?

Any advice would be appreciated! 

Aside from that, the garden is doing well, and starting to get a bit more colourful!

My first tomato flowers have appeared. 

The borage is flowering.

Aaaaand the chickens are still just doing their thing.

Jess