Shares in Elon Musk's SpaceX closed almost 20% higher on their trading debut on Friday after the biggest initial public offering (IPO) in history, making the polarizing entrepreneur the world's first trillionaire as he vowed to take humanity to Mars.

The blockbuster IPO, which raised more than $75 billion, is expected to kick off a series of major IPOs by AI companies in the coming months.

The stock climbed as high as $176, or 31% above its offering price of $135, in its first session before ending the day at $161.50.

"SpaceX wants to be able to take you to the moon, take you to Mars, and ultimately beyond," Musk said at a launch event in Starbase, Texas, surrounded by staff, many of whom became multi-millionaires with the launch of trading.

"I'm confident at this point that with the incredible team that we have here at SpaceX, that we will do that for you," Musk added.

About 100 people assembled outside the Nasdaq's home in New York, where SpaceX also marked the occasion with a neon sign in Times Square.

Musk "sets very futuristic goals that no one else is doing, and I think that has got a lot of people excited," said Sarin Sio, of financial company Dovetail, who had come to the Nasdaq headquarters.

The company priced more than 555 million shares at $135 each in a Thursday filing with the US markets regulator, valuing SpaceX at just under $1.8 trillion.

Friday's gain lifted SpaceX's market value to more than $2 trillion, placing it among the 10 most valuable American companies – ahead of Tesla, Facebook-owner Meta and Walmart.

Options for nearly 83 million additional shares could push the total raised above $86 billion.

Co-founded by Musk in 2002, the rocket startup has since expanded into a major satellite operator and has also folded in Musk's artificial intelligence company xAI, alongside the social media platform X.

Trading under the ticker symbol "SPCX," the conglomerate is being closely watched for how Wall Street absorbs the offering and what it will mean for its AI rivals looking to trade on the public markets as early as this year.

OpenAI and Anthropic have both recently filed initial documents with regulators.

How much money is $1 trillion?

The milestone makes Musk by far the world's richest person – the first trillionaire in human history.

But what does $1 trillion actually look like?

A trillion dollars is roughly equivalent to the annual GDP of countries such as Switzerland or Poland, which is about $1.04 trillion in 2025, according to the International Monetary Fund. It is also around three times the current value of France's gold reserves.

According to The New York Post, if one trillion one-dollar bills, each about 0.0043 inches (about 0.01 centimeters) thick, were stacked on top of each other, the tower would reach more than 67,000 miles (about 107,200 kilometers) high, over one-quarter of the distance between Earth and the moon. Laid end-to-end, with each bill measuring about 6.14 inches in length, the same stack would stretch nearly 4 million miles beyond the distance between Earth and the sun.

NBC News notes that a stack of $100 bills worth $1 trillion would rise about 679 miles high, which is nearly 11 times the distance from Earth to the edge of outer space.

In economic reality, $1 trillion exceeds the combined net worth of five of the world's richest individuals, including Google co-founders Larry Page and Sergey Brin, Amazon founder Jeff Bezos, Meta CEO Mark Zuckerberg, and Oracle co-founder Larry Ellison.

But experts cautioned that Musk's wealth, unlike gold or other tangible assets, is largely tied to stock holdings, making it far more volatile.

"If Elon Musk wanted to sell off a huge chunk of his shares to buy real estate or whatever, the stock price would drop hugely," warned Alexandre Baradez, head of market analysis for investment company IG France, adding the it would also trigger broader investor reactions, further decreasing the stock's value.

(With input from AFP)