Footnotes

• Twitter @Spaceclinics, @Alan_McCall_

• Contributors SM conceived the idea developed from an original concept written by AW. AM reviewed the initial manuscript with AW providing input. SM, AM and AW reviewed the drafts until the final version was submitted.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Commissioned; externally peer reviewed.