The bodies lie as they fell, atop Everest.

The fierce winds and thick frost freeze them in time. Instant rigor mortis. The dead keeping an eternal post atop the roof of the world.

About 200 bodies lie unburied on the mountain's side.

Maria Strydom, a Melbourne climber, university lecturer, wife, is now among their number.

It is unclear if her body will be brought down. Less than a fifth are – the cost, in terms of resources and the risk to others' lives, is often judged too high.

Maria – sometimes self-styled as Marisa – died after severe altitude sickness caused her brain to swell. She and her husband Robert Gropel had reached Camp Four.

Dr Gropel, a vet in Melbourne's north-east, has been evacuated by helicopter from Camp 2 and is now in Kathmandu. His parents flew from Melbourne to Kathmandu on Monday to be with their son, who is battling a build-up of fluid in his lungs, known as a high altitude pulmonary oedema.

The journey to the top of Everest is sign-posted by the marks of the dead, and oftentimes by the bodies. The vast majority lie within the "death zone", the final 400 metres to the top.

More than 4000 people have climbed Everest's 8848 metres since it was first attempted in 1905. According to the Himalayan Database, death rates on the mountain are plummeting - down below 5 per cent, thanks to the advent of modern mountain gear.

The database estimates that on average almost seven people have died climbing the peak each year in the most recent decade.

Between 1950 and 2009, most deaths on the mountain were attributed to falls and avalanches. However, above 8000 metres, inside the death zone, the chances of dying from altitude sickness increase significantly.

Nineteen died at base camp in an earthquake in 2015 that temporarily closed the mountain and killed and another 8000 people in elsewhere in Nepal. In 2014, 15 sherpas died in an avalanche on the slopes.

Last year, National Geographic Magazine asked: Will Everest's climbing circus slow down after the disasters? It did not.

'Green Boots' is among the more famous dead. A bright pair of green ski shoes sticking out of a cave, at 8500 metres. First seen in 2001, in 2015, the BBC mounted an investigation to identify the body, eventually naming a young Indian climber, Tsewang Paljor, as the owner of the distinctive boots. However, other theories abound as to the true identity of the dead climber.

In 2014, the green boots disappeared, presumed buried in the snow.

Yet some suggest the body was blown down the mountain. That has been known to happen.

Hannelore Schmatz's body is also gone. She sat, leaning against her backpack with her eyes wide open, for much of the 80s and 90s, her hair blowing in Everest's gale-force winds.

They may have also seen Francys Arsentiev's flag-draped body. She reached the summit in 1998, but became separated from her husband and climbing partner on the descent, and died. In 2007, a climber who had been present during her death scaled the mountain again so he could cover her prone body with an American flag.

On the way there, Dr Strydom and her husband might have passed through "Rainbow Valley", named after the  number of corpses in bright climbing jackets.

Determined to reach the top as a cyclone approached, Dr Strydom's  small party headed for the summit in darkness.

The air is so thin up there, even with bottled oxygen, some liken it to a slow dying. Others say the body uses up oxygen faster than it can be replaced.

Dr Strydom came close to the summit, before being forced to turn back. She was dead before she could return to Camp Three.

It is not yet clear whether her body will be brought down, or buried in place. Committed to the mountain, the world's highest, the tragic, terrible peak.