International Day of Women and Girls in Science 2019: The female scientists who changed history

February 11 marks International Day of Women and Girls in Science, a day designed to celebrate the often-forgotten achievements of female scientists as well as to encourage and inspire women and girls to make their mark in this male-dominated sphere.

While huge leaps have been made in recent years to combat inequality in science, long-standing biases and gender stereotypes often discourage girls and women away from science related fields.

And while there are women science pioneers of the past and present, many of their discoveries and contributions remain unrecognised, ignored or credited to male scientists, a wrong that International Day of Women and Girls in Science aims to reverse.

Here are some of the female scientists you may never have heard of, but whose contributions to science have made our world a better place.

• Rosalind Franklin

Franklin's invaluable contribution to the discovery of the structure of DNA was largely unrecognised in her short lifetime - she died at just 37 from ovarian cancer.

Franklin's work on the X-ray diffraction images of DNA, particularly Photo 51, while at King's College London led to the discovery of the DNA double helix in 1962.

Despite her crucial contribution to this landmark finding, it was three men, Francis Crick, James Watson and Franklin’s colleague Maurice Wilkins, who received the Nobel Prize for Physiology or Medicine in 1962 for the discovery.

• Marie Curie

Arguably the best known female scientist, Curie discovery of radium and polonium and the huge contribution she made made to fighting cancer has made Madame Curie a household name.

And her place in history is well deserved not least because of her work during World War I when she developed small, portable mobile X-ray units, known as "Petits Curies", that she took to the front to treat wounded soldiers.

She also trained 150 women - including her daughter Irene - to operate the machines in perilous conditions.

Madame Curie was the first woman to win a Nobel Prize - and the first person and only woman to win twice - as well as the only person to win a Nobel Prize in two different sciences.

• Ada Lovelace

The daughter of poet Lord Bryon, Lovelace was a pioneer of computer programming - in fact she's often described as the first computer programmer.

A mathematician and writer, Lovelace published the first algorithm for Victorian all-rounder Charles Babbage's Analytical Engine, considered to be the earliest version of a computer.

This ‘computer’ was just theoretical and was never built and Ada, who died just 36, never saw her programming put into practice.

• Jocelyn Bell Burnell

Astrophysicist Bell's discovery of pulsars, along with her PhD supervisor Antony Hewish, is considered to be one of the greatest astronomical discoveries of the twentieth century.

Bell discovered these rotating neutron stars - so called because they appear to ‘pulse’ as the beam of light they emit can only be seen when it faces the Earth - in 1967 as a postgraduate student.

She noted a signal that pulsed once every second and jokingly named it 'little green men 1' - a nod to alien lifeforms.

Controversially, it was Hewish who received the 1974 Nobel Prize in Physics for his role in the discovery despite the fact it was Bell who first observed the pulsars.

• Rita Levi-Montalcini

Italian Levi-Montalcini won the Nobel Prize in Physiology or Medicine in 1986 for her discovery, along with her colleague Stephen Cohen, of a protein called nerve growth factor (NGF).

Her groundbreaking investigations into how the nervous system develops enabled deeper understanding of medical problems like Alzheimer’s disease, deformities and tumour diseases.

Her work is even more remarkable given she faced considerable obstacles for being a Jewish woman in 1930s Italy.

Barred from a career in research under Mussolini, she decided to set up a laboratory in her bedroom, where she continued her research even after her family were forced to move underground for a year when Germany invaded Italy in 1943.

• Frances Arnold

A chemical engineer, Arnold won the 2018 Nobel Prize in Chemistry for her pioneering work on the evolution of enzymes.

Directed evolution aims to create new and better biological material in the form of enzymes - proteins that catalyse chemical reactions - which allows us to use greener biological manufacturing processes to make fuels, chemicals and materials.

Speaking at a talk last year on women in science, Arnold said: “What I want to do is encourage women to take on this incredibly exciting and fun challenge to use their brains for the benefit of humanity but through science and technology.

“Don’t let the guys have this. This is great, great career material.”

• Tu Youyou

The 88-year-old's discovery has saved millions of lives around the world.

The Chinese scientist was working for a secret government unit in the 1960s known as Mission 523 who were tasked by Chairman Mao to find a cure for malaria.

Inspired by traditional Chinese medicine, Tu found a way to extract a compound called artemisinin from sweet wormwood which had been used to treat fevers in the 5th century.

The active compound appeared to fight malaria-friendly parasites and in a bid to speed up the drugs development, Tu volunteered to be the first human to test it.

An artemisinin-based drug combination is now the go-to malaria treatment globally and has had a huge impact on the health and survival of millions of people.

• Dorothy Crowfoot Hodgkin

Nobel Laureate Dorothy Crowfoot Hodgkin was one of the most outstanding X-ray crystallographers of her time.

Her life’s work determined the molecules in structures including penicillin and vitamin B12, and in 1964 she received a Nobel Prize in Chemistry in 1964, the first British woman to be so honoured.

But perhaps her greatest achievement came five years later when, after 34 years of studying insulin, she was finally able to determine its structure. Her breakthrough made it possible for doctors to develop treatments for controlling diabetes.