Archaeologists (4)

Sir Henry Amsworth, an archaeologist and retired army engineer.  An experienced explorer.

Arthur Billingham, an experienced archaeologist, clever, handsome in a distinguished way, brave to the point of foolhardiness but not rash

Lord Percy Winterton, a young man of scholastic bent and great intellect

Roger Hansworth, a young archaeologist fresh out of Oxford, idealistic and committed

Auxilliary staff (6)

Major Donald McClintock, a Scottish former army surgeon, intemperate, and an angry drunk.  Disgraced by his conduct during the Martian pirate assault on the expedition, which near led to the death of Miss Pennington-Smythe and Major Bastable

Major Oswald Bastable, brother to Captain James Bastable, Oswald is head of security for the Amsworth expedition.

Bob Smithson, quartermaster to the Amsworth expedition, an able man in his early 40s, efficient but not always diligent

Milton Nkome, an African fellow in his early 30s and of surprising adaptability, an old associate of Sir Henry's

Josiah Bladder, a large man in his early 50s, expedition cook, a post obtained by trickery given his limited skills, wounded in a battle with pirates.  Sent back to Syrtis Major on the Sylph.

Mrs Esme Hatchpenny, a woman of easy virtue in her early 30s, blowsy and often drunken, assistant cook introduced by Josiah Bladder.  Sent back, unwillingly, to Syrtis Major on the Sylph.

Family and servants (8)

Mrs Elizabeth Amsworth, Sir Henry's wife, formidable, short, plump and efficient

Kit Amsworth, the Amsworth's daughter, a sporty young thing fresh out of university

Jenkins, Sir Henry's man

Lizzie, Mrs Amsworth's maid

Henley, Lord Winterton's man

Agnes Smithson, Bob Smithson's wife, a friendly and competent woman, also in her 40s

Felicity Bastable, Major Oswald's wife, an intelligent and attractive young woman

Cpl Arnold Smith, Bastable's former batman, an efficient if morose man

Assorted fellows (9)

Tom Bigby, a strongman participating in the expedition for reasons unclear

Oswald Bracewell, an FCO man, seemingly a broken fellow

Miss Harriet Weems, freelance journalist, thin, plain, clumsy and often tactless, but clever and determined

The Black Hand Gang, six fellows of assorted utility (John Black, Bob Critchley, Mike Philton, Phil Garner, Tom Carter, John Reed).  John Reed abandoned his watch for dalliance with Mrs Hatchpenny, so endangering the expedition and leaving it unwarned when the Martian pirate assault came.  Imprisoned for dereliction of duty.

Martians (8)

Haakarla, a Martian guide

Shaamshi, a Martian translator

The Porters, six Martians for carrying bags (named by Sir Henry Tom, Dick, Harry, Bob, Bill, Larry)