SpaceX's $2.1 trillion（約340兆円） market debut vaults it past Tesla, fueling speculation of a merger between Elon Musk's two companies.

What happened: SpaceX completed its initial public offering and closed Friday with a market cap of $2.1 trillion（約340兆円）, becoming the sixth most valuable U.S.-listed company—ahead of Tesla, which had a market cap of $1.52 trillion（約240兆円） as of market close. SpaceX's S-1 filing includes new language warning of potential "significant amount of equity in connection with future transactions," and SpaceX president and COO Gwynne Shotwell said in a CNBC interview that a merger between the two companies "might make Elon's life a little easier."

Why it matters: The combined scale of SpaceX and Tesla would reshape Musk's corporate portfolio and consolidate his control over transportation and space ventures under one public entity. The filing's language and Shotwell's openness suggest a merger is not merely speculation but a genuine possibility being considered by leadership.

What to watch: The S-1 document's warning about future equity issuance—phrased as "a significant amount"—suggests the deal, if pursued, could be substantial and may require approval from investors in both companies.